Comparing methods of clinical measurement: reporting standards for bland and altman analysis

In vitro protamine addition for coagulation assessment using TEG 6s system during cardiopulmonary bypass: a pilot study

OBJECTIVE

Systemic heparinization during cardiopulmonary bypass (CPB) can significantly affect thromboelastography (TEG). This study investigated the feasibility of adding protamine in vitro to allow assessment of coagulation status using the TEG 6s system during CPB.

METHODS

In this prospective observational study, 21 patients undergoing elective cardiac valve surgery were evaluated. During CPB, protamine was added in vitro to the heparinized blood of these patients at a concentration of 0.05 mg/mL and analyzed with the TEG 6s (Pre). The TEG parameters were compared to those analyzed after CPB withdrawal and systemic protamine administration (Post).

RESULTS

The citrated kaolin maximal amplitude (CK-MA) and the citrated functional fibrinogen maximal amplitude (CFF-MA) exhibited strong correlations between Pre and Post measurements (r = 0.790 and 0.974, respectively, P < 0.001 for both), despite significant mean differences (-2.23 mm for CK-MA and -0.68 mm for CFF-MA). Bland-Altman analysis showed a clinically acceptable agreement between Pre and Post measurement of CK-MA and CFF-MA (the percentage error was 10.6% and 12.2%, respectively). In contrast, the citrated kaolin reaction time (CK-R) showed no significant correlation between Pre and Post measurements (r = 0.328, P = 0.146), with a mean difference of 1.42 min (95% CI: -0.45 to 3.29).

CONCLUSIONS

In vitro protamine addition allows assessment of coagulation status during CPB using the TEG 6s system. CK-MA and CFF-MA measured during CPB using this method revealed a strong correlation and agreement with post-CPB measurements, suggesting that our method potentially facilitates early prediction of post-CPB coagulation status and decision-making on transfusion strategies.

CLINICAL TRIAL REGISTRATION

The study was registered in the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR, registration number: UMIN000041097, date of registration: July 13, 2020, https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000046925 ) before the recruitment of participants.

The Ramp protocol: Uncovering individual differences in walking to an auditory beat using TeensyStep

Intentionally walking to the beat of an auditory stimulus seems effortless for most humans. However, studies have revealed significant individual differences in the spontaneous tendency to synchronize. Some individuals tend to adapt their walking pace to the beat, while others show little or no adjustment. To fill this gap we introduce the Ramp protocol, which measures spontaneous adaptation to a change in an auditory rhythmic stimulus in a gait task. First, participants walk at their preferred cadence without stimulation. After several steps, a metronome is presented, timed to match the participant's heel-strike. Then, the metronome tempo progressively departs from the participant's cadence by either accelerating or decelerating. The implementation of the Ramp protocol required real-time detection of heel-strike and auditory stimuli aligned with participants' preferred cadence. To achieve this, we developed the TeensyStep device, which we validated compared to a gold standard for step detection. We also demonstrated the sensitivity of the Ramp protocol to individual differences in the spontaneous response to a tempo-changing rhythmic stimulus by introducing a new measure: the Response Score. This new method and quantification of spontaneous response to rhythmic stimuli holds promise for highlighting and distinguishing different profiles of adaptation in a gait task.

Diagnostic efficacy of hand-held digital refractometer for determining total serum protein in indigenous sheep of Pakistan

The study was designed to ascertain the diagnostic efficacy of hand-held digital refractometer in determining total protein (TP). The Sipli sheep (n = 128) were grouped as per gender (females = 99, males = 29) and age (G1 = up till 1 year, n = 35; G2 = from 1 to 2 years, n = 63; G3 = above 2 years, n = 30). The results regarding the overall mean (±SE) values for the TPs attained through serum chemistry analyzer (TP1) and hand-held digital refractometer (TP2) were non-significantly (P≥0.05) different (59.2±1.6g/L and 59.8±0.5g/L, respectively). However, the reference intervals (RIs) were quite different for the two TPs being 45.1-95.7g/L and 57.0-67.0g/L for TP1 and TP2, respectively. Similar results were seen for gender-wise and group-wise results. On the contrary, the results regarding correlation coefficient and logilinear regression showed a negative correlation between the two TPs (r = -0.0244) with an adjusted r-square of 0.059 (5.9% probability). Furthermore, the three tests implied to assess the level of agreement between the two methods (Cronbach alpha, Intraclass correlation coefficient, and Bland & Altman test) revealed least agreement between the two methods. In a nutshell, the results of TP through digital refractometer were not in concordance with those attained through serum chemistry analyzer. However, it can cautiously be used if these results are compared with relevant corrected RIs.

Assessment of Ground Contact Time in the Field: Evaluation of Validity and Reliability

ABSTRACT

Weber, JA, Hart, NH, Rantalainen, T, Connick, M, and Newton, RU. Assessment of ground contact time in the field: evaluation of validity and reliability. J Strength Cond Res 38(1): e34-e39, 2024-The capacity to measure the kinetic and kinematic components of running has been extensively investigated in laboratory settings. Many authors have produced work that is of high value to practitioners within sporting environments; however, the lack of field-based technology to assess features of running gait validly and reliably has prevented the application of these valuable works. This paper examines the validity and reliability of a practical field-based methodology for using commercial inertial measurement units (IMUs) to assess ground contact time (GCT). Validity was examined in the comparison of GCT measured from ground reaction force by a force plate and that determined by a lumbar mounted commercial IMU and analyzed using a commercially available system (SPEEDSIG). Reliability was assessed by a field-based examination of within and between-session variability in GCT measured using a commercially available system (SPEEDSIG). Significance was set at p ≤ 0.05. Results for validity (intraclass correlation [ICC] 0.83) and reliability (ICC 0.91) confirm that the described field-based methodology is qualified for use to determine GCT in a practical setting. The implications of this study are important as they offer sport practitioners (S&C coaches, rehab specialists, and physios) a scalable method to assess GCT in the field to develop greater understanding of their athletes and improve performance, injury prevention, and rehabilitation interventions. Furthermore, these results provide the foundation for further work that could provide greater detail describing individual running gait in the field.

Comparing Non-Invasive Spectrophotometry to Hematology Analysis for Hemoglobin Measurements in Sickle Cell Disease Patients

Patients with sickle cell disease (SCD) require repeated blood sampling for hemoglobin (Hb) concentration measurements. The primary aim of this study was to compare non-invasive spectrophotometric hemoglobin (SpHb, g/dL) measurements to those taken via an automated hematology analyzer (Hb, g/dL) in patients with SCD visiting outpatient clinics and to investigate the correlations and agreements between both measurement techniques. Secondarily, we aimed to identify the SpHb cut-off concentration for the diagnosis of anemia and to monitor the effects of the pleth variability index (PVI, %) and perfusion index (PI) on SpHb measurements. The results gained from the examination of one hundred and fifty-eight patients indicated that the SpHb measurements overestimated the lab Hb concentrations, with a mean (SpHb-Hb) bias of 0.82 g/dL (SD 1.29). The SpHb measurements were positively correlated with the Hb measurements (Kendall's tau correlation (τ), n = 158, τ = 0.68, p < 0.001), with an intra-class correlation (ICC) of 0.67 and a 95% CI from 0.57 to 0.74 (p = 0.000). The SpHb cut-off concentration to diagnose anemia was 11.4 and 11.7 g/dL for males and females, respectively. SpHb sensitivity was low for males and females at 64.4% and 57.1%; however, the specificity was higher at 90.9% and 75%, with positive predictive values (PPVs) of 95.6 and 85.7, respectively. No correlation existed between SpHb measurements and the PVI (%) in contrast with a moderate correlation with the PI (r = 0.049, p = 0.54, and r = 0.36, p < 0.001, respectively). The mean PI was low at 2.52 ± 1.7. In conclusion, the SpHb measurements were consistently higher than the lab Hb concentrations, with a positive correlation. The sensitivity and precision of the SpHb measurements were lower than expected. However, the SpHb specificity and its positive predictive values (PPVs) indicated that it is less likely for a patient with a positive SpHb test result for anemia to be non-anemic. These results will allow SpHb measurement to play a role in excluding the presence of anemia. In light of the low PI values determined, the SpHb measurements were challenging to take and, thus, require further technological improvements.

Inter-observer variation in two-dimensional and three-dimensional ultrasound measurement of papillary thyroid microcarcinoma

BACKGROUNDS

The reliable ultrasound (US) measurements of papillary thyroid microcarcinoma (PTMC) are very important during active surveillance. This prospective study was design to investigate the inter-observer reliability and agreement of two- dimensional ultrasound(2DUS) and three-dimensional ultrasound(3DUS) in the measurement of maximum diameter and volume for PTMC.

METHODS

This prospective study included 51 consecutive patients with solitary PTMC confirmed by biopsy. Two independent observers performed measurements of each tumor using a standardized measurement protocol. The maximum diameter was the largest one of the three diameters measured on the largest transverse and longitudinal 2DUS images. 2DUS volume was calculated using ellipsoid formula method. The virtual organ computer aided analysis(VOCAL) was used to determine 3DUS volume. The inter-observer reliability was assessed using intraclass correlation coefficient(ICC) with 95% confidence intervals(CIs). Bland-Altman analysis was used to evaluate agreement, and expressed as a bias with 95% limits of agreement(LOA).

RESULTS

The maximum diameter was 0.78 ± 0.14 cm. Volume measured by 3DUS was significantly smaller than that by 2DUS(0.163 ± 0.074 cm3 vs. 0.175 ± 0.078 cm3, P = 0.005). The ICCs of inter-observer reliability of maximum diameter, 2DUS volume and 3DUS volume was 0.922(0.864-0.955), 0.928(0.874-0.959), and 0.974(0.955-0.985), respectively. The ICCs of 2DUS and 3DUS volume was 0.955(0.909-0.976). The inter-observer agreement of maximum diameter, 2DUS volume and 3DUS volume was 1.096(0.7322 to 1.459), 1.008(0.5802-1.435), and 1.011(0.7576-1.265), respectively. The inter-observer agreement of 2DUS and 3DUS volume was 1.096(0.7322 to 1.459).

CONCLUSION

Maximum diameter had the lowest degree of observer variation among all the measurements. Volume measured by 3DUS had lower variability and higher repeatability than that by 2DUS, which might be helpful to provide more reliable estimates of tumor size for PTMC.

Can Non-Invasive Spectrophotometric Hemoglobin Replace Laboratory Hemoglobin Concentrations for Preoperative Anemia Screening? A Diagnostic Test Accuracy Study

Preoperative assessment of hemoglobin concentration in blood is important to diagnose anemia. The primary aim of this prospective diagnostic test accuracy study was to monitor non-invasive spectrophotometric hemoglobin (SpHb, g/dL) concentrations among adults prior to elective surgery and to investigate the correlation and agreement of SpHb with laboratory hemoglobin (Hb, g/dl). A secondary aim was to identify the anemia cut-off values for SpHb based on the World Health Organization (WHO) definitions for anemia. This study included 151 consecutive patients (age ≥ 18 year) presenting for preoperative evaluation prior to scheduled elective general or orthopedic surgery. Results identified the mean ± SD of SpHb at 11.43 ± 2.01 g/dL, which underestimated the mean laboratory Hb (12.64 ± 2.29 g/dL, p < 0.001). A bias mean difference (SpHb-Hb) of -1.21 g/dL, with a SD of 1.76, was reported. This bias (SpHb-Hb) was inversely correlated with the mean Hb concentrations. A positive correlation existed between SpHb and Hb, with a good degree of reliability and a significant Intra Class Correlation (ICC). SpHb diagnosed anemia in 32.3% and 60.3% of males and females, respectively. The SpHb cut-off values to identify anemia were 11.3 and 10.2 g/dL for males and females, respectively, with a sensitivity of 83.3% for males and only 62.9% for females. The specificity for males and females were 81% and 91.3%, respectively. SpHb sensitivity allows for anemia diagnosis among males, but not females. However, the specificity allows SpHb to rule out anemia for both.

Interrater reliability for the detection of cortical lesions on phase-sensitive inversion recovery magnetic resonance imaging in patients with multiple sclerosis

Objective

To assess the reliability of phase-sensitive inversion recovery (PSIR) magnetic resonance imaging (MRI) and its accuracy for determining the topography of demyelinating cortical lesions in patients with multiple sclerosis (MS).

Materials and Methods

This was a cross-sectional study conducted at a tertiary referral center for MS and other demyelinating disorders. We assessed the agreement among three raters for the detection and topographic classification of cortical lesions on fluid-attenuated inversion recovery (FLAIR) and PSIR sequences in patients with MS.

Results

We recruited 71 patients with MS. The PSIR sequences detected 50% more lesions than did the FLAIR sequences. For detecting cortical lesions, the level of interrater agreement was satisfactory, with a mean free-response kappa (κFR) coefficient of 0.60, whereas the mean κFR for the topographic reclassification of the lesions was 0.57. On PSIR sequences, the raters reclassified 366 lesions (20% of the lesions detected on FLAIR sequences), with excellent interrater agreement. There was a significant correlation between the total number of lesions detected on PSIR sequences and the Expanded Disability Status Scale score (ρ = 0.35; p < 0.001).

Conclusion

It seems that PSIR sequences perform better than do FLAIR sequences, with clinically satisfactory interrater agreement, for the detection and topographic classification of cortical lesions. In our sample of patients with MS, the PSIR MRI findings were significantly associated with the disability status, which could influence decisions regarding the treatment of such patients.

Mass Spectrometry-Based Evaluation of the Bland-Altman Approach: Review, Discussion, and Proposal

Reliable quantification in biological systems of endogenous low- and high-molecular substances, drugs and their metabolites, is of particular importance in diagnosis and therapy, and in basic and clinical research. The analytical characteristics of analytical approaches have many differences, including in core features such as accuracy, precision, specificity, and limits of detection (LOD) and quantitation (LOQ). Several different mathematic approaches were developed and used for the comparison of two analytical methods applied to the same chemical compound in the same biological sample. Generally, comparisons of results obtained by two analytical methods yields different quantitative results. Yet, which mathematical approach gives the most reliable results? Which mathematical approach is best suited to demonstrate agreement between the methods, or the superiority of an analytical method A over analytical method B? The simplest and most frequently used method of comparison is the linear regression analysis of data observed by method A (y) and the data observed by method B (x): y = α + βx. In 1986, Bland and Altman indicated that linear regression analysis, notably the use of the correlation coefficient, is inappropriate for method-comparison. Instead, Bland and Altman have suggested an alternative approach, which is generally known as the Bland-Altman approach. Originally, this method of comparison was applied in medicine, for instance, to measure blood pressure by two devices. The Bland-Altman approach was rapidly adapted in analytical chemistry and in clinical chemistry. To date, the approach suggested by Bland-Altman approach is one of the most widely used mathematical approaches for method-comparison. With about 37,000 citations, the original paper published in the journal The Lancet in 1986 is among the most frequently cited scientific papers in this area to date. Nevertheless, the Bland-Altman approach has not been really set on a quantitative basis. No criteria have been proposed thus far, in which the Bland-Altman approach can form the basis on which analytical agreement or the better analytical method can be demonstrated. In this article, the Bland-Altman approach is re-valuated from a quantitative bioanalytical perspective, and an attempt is made to propose acceptance criteria. For this purpose, different analytical methods were compared with Gold Standard analytical methods based on mass spectrometry (MS) and tandem mass spectrometry (MS/MS), i.e., GC-MS, GC-MS/MS, LC-MS and LC-MS/MS. Other chromatographic and non-chromatographic methods were also considered. The results for several different endogenous substances, including nitrate, anandamide, homoarginine, creatinine and malondialdehyde in human plasma, serum and urine are discussed. In addition to the Bland-Altman approach, linear regression analysis and the Oldham-Eksborg method-comparison approaches were used and compared. Special emphasis was given to the relation of difference and mean in the Bland-Altman approach. Currently available guidelines for method validation were also considered. Acceptance criteria for method agreement were proposed, including the slope and correlation coefficient in linear regression, and the coefficient of variation for the percentage difference in the Bland-Altman and Oldham-Eksborg approaches.

Comparison of mainstream end tidal carbon dioxide on Y-piece side versus patient side of heat and moisture exchanger filters in critically ill adult patients: a prospective observational study

The purpose of the study was to investigate the accuracy of mainstream EtCO2 measurements on the Y-piece (filtered) side of the heat and moisture exchanger filter (HMEF) in adult critically ill patients, compared to that on the patient (unfiltered) side of HMEF. We conducted a prospective observational method comparison study between July 2019 and December 2019. Critically ill adult patients receiving mechanical ventilation with HMEF were included. We performed a noninferiority comparison of the accuracy of EtCO2 measurements on the two sides of HMEF. The accuracy was measured by the absolute difference between PaCO2 and EtCO2. We set the non-inferiority margin at + 1 mmHg in accuracy difference between the two sides of HMEF. We also assessed the agreement between PaCO2 and EtCO2 using Bland-Altman analysis. Among thirty-seven patients, the accuracy difference was - 0.14 mmHg (two-sided 90% CI - 0.58 to 0.29), and the upper limit of the CI did not exceed the predefined margin of + 1 mmHg, establishing non-inferiority of EtCO2 on the Y-piece side of HMEF (P for non-inferiority < 0.001). In the Bland-Altman analyses, 95% limits of agreement between PaCO2 and EtCO2 were similar on both sides of HMEF (Y-piece side, - 8.67 to  + 10.65 mmHg; patient side, - 8.93 to  + 10.67 mmHg). The accuracy of mainstream EtCO2 measurements on the Y-piece side of HMEF was noninferior to that on the patient side in critically ill adults. Mechanically ventilated adult patients could be accurately monitored with mainstream EtCO2 on the Y-piece side of the HMEF unless their tidal volume was extremely low.

Measurement of Cardiac Output Using an Ultrasonic Cardiac Output Monitor (USCOM) in Patients with Single-Ventricle Physiology

We evaluate the validity of cardiac index (CI) measurements utilizing the Ultrasonic Cardiac Output Monitor (USCOM), a non-invasive Doppler ultrasound device, by comparing measurements to cardiac catheterization-derived CI measurements in patients with single-ventricle physiology. USCOM measurements were repeated three times for each patient at the beginning of a cardiac catheterization procedure for twenty-six patients undergoing elective pre-Glenn or pre-Fontan catheterization. CI was measured by USCOM and was calculated from cardiac catheterization data using Fick's method. Bland-Altman analysis for CI showed bias of 0.95 L/min/m² with the 95% limits of agreement of - 1.85 and 3.75. Pearson's correlation coefficient was 0.89 (p < 0.001) indicating a strong positive relationship between USCOM and cardiac catheterization CI measurements. When excluding two patients with significant dilation of the neo-aortic valve (z-score >  + 5), the bias improved to 0.66 L/min/m² with the 95% limits of agreement of - 1.38 and 2.70. Percent error of limits of agreement was 34%. There was excellent intra-operator reproducibility of USCOM CI measurements with an intra-class coefficient of 0.96. We demonstrate the use of USCOM to measure CI in patients with single-ventricle physiology for the first time, showing acceptable agreement of the CI measurements between USCOM and cardiac catheterization with a high intra-operator reproducibility.

Development and validation of the ND10 to measure neck-related functional disability

BACKGROUND

Previous neck-specific patient-reported outcome measures (PROMs) have tended to measure both symptoms and disability. This multi-staged study developed and evaluated a neck-specific PROM focusing on functional disability.

METHODS

This study integrated findings from systematic reviews on neck-specific outcome measures, patient interviews, qualitative studies on neck disability, and iterative item testing to develop a 10-item measure of neck-related disability (ND10). Content validity was assessed by classifying items using the International Classification of Functioning, Disability and Health (ICF) and perspective linking. Patients (n = 78) with neck pain completed cognitive interviews, exploring items of the Neck Disability Index (NDI) and ND10, and completed structured questions related to literacy and relevance. Test-retest reliability and internal consistency were evaluated using intraclass correlation coefficients, Bland Altman graphs, and Cronbach's alpha. Concurrent convergent validity was evaluated by comparing the ND10 to the NDI, Single Assessment Numeric Evaluation (SANE), and Disabilities of the Arm, Shoulder and Hand (DASH). Known group validity was determined by comparing ND10 scores from patients, who rated their neck as more or less than 1/2 of "normal" on the SANE, using t-tests.

RESULTS

The ND10 requires respondents to make rational judgements about their neck-related body function and disability. It has high internal consistency (0.94) and re-test reliability (0.87; SEM = 3.2/100; MDC = 7.5); and no re-test bias (mean re-test difference of 0.6). It followed expected correlation patterns, being highly correlated with related multi-item PROMs (r = 0.85-0.91), and moderately correlated to the single-item SANE. More patients agreed that the ND10 was easily readable than did so for the NDI (84% vs 68%; p < 0.05). All the PROMs distinguished the patients who perceived themselves as being abnormal/normal defined by a dichotomized SANE (p < 0.01).

CONCLUSION

The ND10 is reliable and valid for measuring neck-related functional disability. Longitudinal and cross-cultural translation studies are needed to support future use.

Evaluation of the accuracy of a non-invasive hemoglobin-monitoring device in schoolchildren

BACKGROUND

Iron deficiency anemia (IDA) is a public health problem in children and adolescents that is characterized by reduced hemoglobin (Hb) levels. Non-invasive monitoring devices can measure Hb levels continuously without pain or discomfort; however, little is known about their accuracy in children and adolescents. This study estimated the accuracy of a non-invasive Hb monitor in this age group.

METHODS

Participants were outpatients visiting the Tokyo Metropolitan Children's Medical Center for blood tests between January and March 2019. Hb levels were measured using both non-invasive Astrim Fit monitoring devices and invasive blood collection followed by automated analysis. Bland-Altman analysis assessed the agreement between the two measurements.

RESULTS

Overall, 120 schoolchildren (9-15 years old, 51 % female) were enrolled. The non-invasive measuring device recorded Hb levels of 13.5 ± 1.6 g/dL (mean ± standard deviation [SD]), while the mean Hb level obtained from the collected blood was 13.7 ± 1.7 g/dL. Therefore, the mean difference of bias and SD of precision was 0.17 ± 1.95 g/dL. Values of lower and upper limits of agreement were -3.65 and 3.99, respectively. There was no systematic fixed or proportion bias. Fifty-nine participants (49 %) had a relative error of ± 0.10.

CONCLUSION

The Astrim Fit non-invasive Hb monitor can be used to evaluate Hb levels among schoolchildren for health promotion or research purposes because of its extremely low bias (or precision), no systematic biases (including fixed or proportion biases), and positive correlation between non-invasive monitoring and blood drawing. However, it is difficult to assess Hb levels in children and adolescents using the Astrim Fit device for diagnostic purposes.

Contrast-enhanced ultrasound is a reliable and reproducible assessment of necrotic ablated volume after radiofrequency ablation for benign thyroid nodules: a retrospective study

PURPOSE

To investigate the intra- and inter-observer reliability and agreement of contrast-enhanced ultrasound (CEUS) in measuring ablated volume (Va) after radiofrequency ablation (RFA) for benign thyroid nodules.

MATERIALS

This retrospective study evaluated 65 patients with 74 benign thyroid nodules who underwent RFA. Patients were followed up at 1, 3, 6, and 12 months and every 12 months thereafter. Two independent observers measured the Va using CEUS during the same follow-up visit. The intra- and inter-observer reliability was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval. The Bland-Altman analysis was used to evaluate the inter-observer agreement, which was expressed as a mean difference with 95% limit of agreement (LOA).

RESULTS

No significant difference was found in Va measurements by the two observers with a mean follow-up time of 41.17 ± 16.80 months (all p > 0.05). The intra- and inter-observer reliability were both excellent (ICC >0.90) at each follow-up period. The 95% LOA became wider over the follow-up period. The smallest 95% LOA was found at 1 month with a LOA from 0.8117 to 1.122, and the largest 95% LOA was from 0.5694 to 1.343 at 36 months.

CONCLUSIONS

CEUS could provide a reliable and reproducible assessment of Va after RFA for benign thyroid nodules. In clinical post-ablation follow-up, the irregular morphology of ablated area and the variation by different observers could not affect the assessment of Va by CEUS.

Evaluation of the reliability of lower extremity alignment measurements using EOS imaging system while standing in an even weight-bearing posture

This study aimed to analyze the reproducibility and reliability of the alignment parameters measured using the EOS image system in both limbs while standing with an even weight-bearing posture. Overall, 104 lower extremities in 52 patients were analyzed retrospectively. The patients stood with an even load over both lower extremities then rotated 15° in both directions. Two EOS images were acquired and 104 pairs of lower extremities were compared according to the position of the indexed lower extremities. Then, the inter-observer reliability of the EOS system and the inter-modality reliability between EOS and computed tomography (CT) were evaluated. Femoro-tibial rotation (FTR) and tibial torsion demonstrated a significant difference between the anterior and posterior positions of the indexed lower extremity. In the inter-observer reliability analysis, all values except for FTR and tibial torsion demonstrated good or very good reliability. In the anterior position, FTR demonstrated moderate, and tibial torsion demonstrated poor reliability. In the posterior position, both FTR and tibial torsion demonstrated poor reliability. In the reliability analysis between the three-dimensional (3D) EOS model and 3D CT images, all measurements of the femur demonstrated very good reliability, but measurements of the tibia did not. For the coronal and sagittal alignment parameters measured by the EOS 3D system with rotated standing posture, except for the measurement including tibial torsion., there were no significant difference for either position of the indexed extremities with high agreement between the observers as well as with the CT 3D model.

Noninvasive cardiac output measurement is inaccurate in patients with severe aortic valve stenosis undergoing transcatheter aortic valve implantation

Background

Noninvasive cardiac output (CO) measured using ClearSight™ eliminates the need for intra-arterial catheter insertion. The purpose of this study was to examine the accuracy of non-invasive CO measurement in patients with severe aortic stenosis (AS).

Methods

Twenty-eight patients undergoing elective transcatheter aortic valve implantation were prospectively enrolled in this study. The CO was simultaneously measured twice before and twice after valve deployment (total of four times) per patient, and the CO was compared between the ClearSight (CO_ClearSight) system and the pulmonary artery catheter (PAC) thermodilution (CO_TD) method as a reference. The Bland-Altman analysis was used to compare the percentage errors between the methods.

Results

A total of 112 paired data points were obtained. The percentage error between the CO_ClearSight and CO_TD was 43.1%. The paired datasets were divided into the following groups according to the systemic vascular resistance index (SVRI): low (< 1,200 dyne s/cm⁵/m²) and normal (1,200–2,500 dyne s/cm⁵/m²). The percentage errors were 44.9% and 49.4%, respectively. The discrepancy of CO between CO_ClearSight and CO_TD was not significantly correlated with SVRI (r = −0.06, P < 0.001). The polar plot analysis showed the trending ability of the CO_ClearSight after artificial valve deployment was 51.1% which below the acceptable cut-off (92%).

Conclusions

The accuracy and the trending ability of the ClearSight CO measurements were not acceptable in patients with severe AS. Therefore, the ClearSight system is not interchangeable with the PAC thermodilution for determining CO in this population.

Cardiac Output Determination in Precapillary Pulmonary Hypertension: A Systematic Review

BACKGROUND

Cardiac output determination is essential in precapillary pulmonary hypertension. While direct Fick is the gold standard, thermodilution is commonly used as the reference method. Moving to noninvasive methods would be highly beneficial for patients, avoiding repetitive invasive assessments. This systematic review followed 3 objectives: (1) assessing the validity of indirect Fick and thermodilution in precapillary pulmonary hypertension, (2) assessing the interchangeability of noninvasive cardiac output measurement methods against reference methods in precapillary pulmonary hypertension, and (3) detecting methodological heterogeneity in the included studies.

METHODS

We systematically reviewed the literature using medical databases and following PRISMA guidelines. We included articles comparing an invasive or noninvasive cardiac output measurement method with thermodilution or direct Fick in precapillary pulmonary hypertension patients. Cutoffs of limits of agreement and percentage error derived from the Bland and Altman graph were used to accept interchangeability. To study methodological heterogeneity, we extracted 9 quality criteria from all studies.

RESULTS

Eleven studies were included. None reached the suggested interchangeability criteria. The median number of the 9 assessed quality criteria was 2 with interquartile range (0-4).

CONCLUSIONS

Further studies evaluating the reliability of thermodilution and the consequences of its use in precapillary pulmonary hypertension patients are necessary. No evidence supports the use of indirect Fick in precapillary pulmonary hypertension. The studied noninvasive methods could not be considered interchangeable with invasive methods. A robust methodology should be used to draw sensible conclusions.

Inter-observer reliability in ultrasound measurement of benign thyroid nodules in the follow-up of radiofrequency ablation: a retrospective study

PURPOSE

To investigate the inter-observer reliability of ultrasound (US) measurement in volume and volume reduction rate (VRR) of benign thyroid nodules during the follow-up of radiofrequency ablation (RFA).

MATERIALS

This retrospective study evaluated 76 patients with 88 benign thyroid nodules who underwent RFA. Two independent observers performed the US measurements during the same follow-up visit. The Bland-Altman analysis was used to evaluate the inter-observer reliability of volume and VRR (logarithmic transformation). The mean difference and 95% limits-of-agreement (LOA) were obtained after antilogarithm.

RESULTS

No significant differences were found in the volume and VRR measurements during a mean follow-up time of 35.52 ± 12.82 months. After antilogarithms, the mean difference of volume was 0.9961, 0.9987, 1.0016, 0.9972, 0.9977 and 0.9969 at 1, 3, 6, 12, 24 and 36 months, respectively. The 95% LOA of volume became wider over the follow-up period, and the largest one was between 0.8471 and 1.1733 at 36 months. The 95% LOA of VRR became narrower over the follow-up period, and the largest one was between 0.9541 and 1.0469 at 1 month. The incidence of regrowth was 20.45% and the largest 95% LOA of regrowth nodules was between 0.9028 and 1.284 at 12 months. At the same follow-up period, VRR had a narrower 95% LOA than volume. Compared with volume ≥10 ml, nodules <10 ml revealed a larger 95% LOA in both the volume and VRR.

CONCLUSION

The inter-observer reliability of the US measurements of benign thyroid nodules during the follow-up period of RFA was acceptable. The variation by different observers could not affect the evaluation of efficacy.

Non-enhanced ultrasound is not a satisfactory modality for measuring necrotic ablated volume after radiofrequency ablation of benign thyroid nodules: a comparison with contrast-enhanced ultrasound

OBJECTIVE

To investigate the intra- and inter-observer reliability and agreement between gray-scale and Doppler ultrasound (US) and contrast-enhanced ultrasound (CEUS) in measuring ablated volume (Va) after radiofrequency ablation (RFA) for benign thyroid nodules.

METHODS

A total of 173 patients with 190 benign thyroid nodules who underwent RFA were included in this study. After RFA, the total volume of ablated nodule was divided into Va and the incompletely treated vital volume. Patients were followed up at 1, 3, 6, 12 months, and every 12 months thereafter. Two independent observers measured Va using US and CEUS during the same follow-up visit. The intra- and inter-observer reliability of the two measurement modalities was assessed using intraclass correlation coefficient (ICC) with 95% confidence interval. The Bland-Altman analysis was used to evaluate agreement, which was expressed as a mean difference with 95% limits of agreement (LOA).

RESULTS

The mean follow-up time was 23.17 ± 12.70 months. Va measured by US was significantly larger than by CEUS (p < 0.001). The intra- and inter-observer reliability decreased over the follow-up period and became moderate in both subgroups at 12 months (all ICC < 0.75). The mean difference and LOA became larger and wider during the follow-up. The best agreement was found in nodules < 10 ml at 1 month with a mean difference of 1.166 and LOA between 0.413 and 3.294.

CONCLUSIONS

The intra- and inter-observer reliability and agreement of US and CEUS in measuring Va were unsatisfactory. CEUS should be considered when Va was needed for further evaluation or in the case of nodules with suspected regrowth.

KEY POINTS

• Va measured by gray-scale and Doppler US was significantly larger than that by CEUS. • Va measured by gray-scale and Doppler US lacked intra- and inter-observer reliability and agreement with CEUS. • CEUS should be preceded to gray-scale and Doppler US for the measurement of Va.

Interobserver agreement issues in radiology

Agreement between observers (i.e., inter-rater agreement) can be quantified with various criteria but their appropriate selections are critical. When the measure is qualitative (nominal or ordinal), the proportion of agreement or the kappa coefficient should be used to evaluate inter-rater consistency (i.e., inter-rater reliability). The kappa coefficient is more meaningful that the raw percentage of agreement, because the latter does not account for agreements due to chance alone. When the measures are quantitative, the intraclass correlation coefficient (ICC) should be used to assess agreement but this should be done with care because there are different ICCs so that it is important to describe the model and type of ICC being used. The Bland-Altman method can be used to assess consistency and conformity but its use should be restricted to comparison of two raters.

Reproducibility and repeatability of identifying the latest electrical activation during mapping of coronary sinus branches in CRT recipients

INTRODUCTION

Studies have shown an association between the outcome in cardiac resynchronization therapy (CRT) and longer interventricular delay at the site of the left ventricular (LV) lead. Targeted LV lead placement at the latest electrically activated segment increases LV function further as compared with standard treatment. We aimed to determine reproducibility and repeatability of identifying the latest electrically activated segment during mapping of all available coronary sinus (CS) branches in patients receiving CRT.

METHODS

We included 35 patients who underwent CRT implantation with protocolled mapping guided LV lead implantation aiming for the site of the latest electrical activation. Three different doctors experienced in electrophysiology and implantation of CRT devices independently measured time interval from the local bipolar right ventricular (RV) electrogram (EGM) to the local unipolar LV EGM at all mapped sites (RV-LV). The segment with the latest electrical activation was defined as the target segment (TS) and the CS tributary containing TS was defined as the target vein (TV). Weighted κ statistics with 95% confidence intervals were computed to assess intra- and interobserver agreement for TS and TV.

RESULTS

We mapped 258 segments within 131 veins. Weighted κ values for repeatability were 0.85 (0.81-0.89) for TS and 0.92 (0.89-0.93) for TV, and weighted κ values of interobserver agreement ranged from 0.70 (0.61-0.73) to 0.80 (0.76-0.83) for TS and 0.73 (0.64-0.78) to 0.86 (0.83-0.89) for TV among all three observers.

CONCLUSION

The reproducibility and repeatability of identifying the latest electrically activated segment during mapping of all available CS branches in patients receiving CRT range from good to very good.

Proposed Modifications in the 6-Minute Walk Test for Potential Application in Patients With Mild COVID-19: A Step to Optimize Triage Guidelines

Supplemental Digital Content is available in the text.

Can measurements from an anteroposterior radiograph predict pelvic sagittal inclination?

Pelvic sagittal inclination (PSI) is often evaluated in patients with hip pathology using lateral radiographs. However, it would be useful if PSI could be predicted from an anteroposterior radiograph since this film is ubiquitous in the evaluation of hip pathology. Herein, computer-modeling was applied to predict PSI from radiographic measurements assessed in the anteroposterior plane. Three-dimensional surface models of the pelvis, femur, and sacrum were reconstructed from computed tomography images of 50 women with hip dysplasia. This study cohort was selected as changes in PSI alter femoral head coverage, which is relevant to the diagnosis and treatment of hip dysplasia, a known cause of hip osteoarthritis. Five radiographic parameters commonly used to independently estimate PSI were evaluated after bone surfaces were projected to an anteroposterior plane, including the symphysis to sacrococcygeal joint distance (S-S distance), the pelvic foramen aspect ratio (PF ratio), the distance between the symphysis and a line connecting the femoral head centers (S-H distance), the sacro-femoral-pubic angle (SFP angle), and the pelvic vertical ratio (PVR). Regression models determined the ability of these parameters to predict PSI from -20° to 20° at 1° increment. All five parameters showed a strong correlation with the PSI (all r > 0.9). From the regression models, PSI was estimated with a median (maximum) absolute error of 3.6° (18.4°), 3.8° (17.7°), 5.2° (17.9°), 5.8° (28.8°), and 3.2° (23.5°) for the S-S distance, PF ratio, S-H distance, SFP angle, and PVR, respectively. The regression model for S-S distance had a mean slope of 2.18 that ranged from 1.98 to 2.41 when the sacrococcygeal joint was located superior to the symphysis. Results indicated that substantial errors occur when estimating the actual value of PSI from an anteroposterior radiograph. However, the change in PSI could be estimated from the S-S distance, which may aid surgeons to successfully increase head coverage through periacetabular osteotomy and to locate the acetabular cup in a functional position for total hip arthroplasty.

Use and reporting of Bland-Altman analyses in studies of self-reported versus measured weight and height

BACKGROUND/OBJECTIVES

Bland-Altman methods for assessing the agreement between two measures are highly cited. However, these methods may often not be used to assess agreement, and when used, they are not always presented or interpreted correctly. Our objective was to evaluate the use and the quality of reporting of Bland-Altman analyses in studies that compare self-reported with measured weight and height.

METHODS

We evaluated the use of Bland-Altman methods in 394 published articles that compared self-reported and measured weight and height data for adolescents or adults. Six reporting criteria were developed: assessment of the normality of the distribution of differences, a complete and correctly labeled Bland-Altman plot displaying the mean difference and limits of agreement (LOA), numerical values and confidence intervals, standard errors, or standard deviations for mean difference, numerical values of LOA, confidence intervals for LOA, and prespecified criteria for acceptable LOA.

RESULTS

Only 72/394 (18%) studies comparing self-reported with measured weight and height or BMI used some form of Bland-Altman analyses. No study using Bland-Altman analyses satisfied more than four of the six criteria. Of the 72 studies, 64 gave mean differences along with confidence intervals or standard deviations, 55 provided complete Bland-Altman plots that were appropriately labeled and described, 37 provided numerical values for LOA, 4 reported that they examined the normality of the distribution of differences, 3 provided confidence intervals for LOA, and 3 had prespecified criteria for agreement.

CONCLUSIONS

Bland-Altman methods appear to be infrequently used in studies comparing measured with self-reported weight, height, or BMI, and key information is missing in many of those that do use Bland-Altman methods. Future directions would be defining acceptable LOA values and improving the reporting and application of Bland-Altman methods in studies of self-reported anthropometry.

Reporting Standards for a Bland-Altman Agreement Analysis: A Review of Methodological Reviews

The Bland-Altman Limits of Agreement is a popular and widespread means of analyzing the agreement of two methods, instruments, or raters in quantitative outcomes. An agreement analysis could be reported as a stand-alone research article but it is more often conducted as a minor quality assurance project in a subgroup of patients, as a part of a larger diagnostic accuracy study, clinical trial, or epidemiological survey. Consequently, such an analysis is often limited to brief descriptions in the main report. Therefore, in several medical fields, it has been recommended to report specific items related to the Bland-Altman analysis. The present study aimed to identify the most comprehensive and appropriate list of items for such an analysis. Seven proposals were identified from a MEDLINE/PubMed search, three of which were derived by reviewing anesthesia journals. Broad consensus was seen for the a priori establishment of acceptability benchmarks, estimation of repeatability of measurements, description of the data structure, visual assessment of the normality and homogeneity assumption, and plotting and numerically reporting both bias and the Bland-Altman Limits of Agreement, including respective 95% confidence intervals. Abu-Arafeh et al. provided the most comprehensive and prudent list, identifying 13 key items for reporting (Br. J. Anaesth. 2016, 117, 569-575). An exemplification with interrater data from a local study accentuated the straightforwardness of transparent reporting of the Bland-Altman analysis. The 13 key items should be applied by researchers, journal editors, and reviewers in the future, to increase the quality of reporting Bland-Altman agreement analyses.

Clinical applicability of the Feline Grimace Scale: real-time versus image scoring and the influence of sedation and surgery

Background

The Feline Grimace Scale (FGS) is a facial expression-based scoring system for acute pain assessment in cats with reported validity using image assessment. The aims of this study were to investigate the clinical applicability of the FGS in real-time when compared with image assessment, and to evaluate the influence of sedation and surgery on FGS scores in cats.

Methods

Sixty-five female cats (age: 1.37 ± 0.9 years and body weight: 2.85 ± 0.76 kg) were included in a prospective, randomized, clinical trial. Cats were sedated with intramuscular acepromazine and buprenorphine. Following induction with propofol, anesthesia was maintained with isoflurane and cats underwent ovariohysterectomy (OVH). Pain was evaluated at baseline, 15 min after sedation, and at 0.5, 1, 2, 3, 4, 6, 8, 12 and 24 h after extubation using the FGS in real-time (FGS-RT). Cats were video-recorded simultaneously at baseline, 15 min after sedation, and at 2, 6, 12, and 24 h after extubation for subsequent image assessment (FGS-IMG), which was performed six months later by the same observer. The agreement between FGS-RT and FGS-IMG scores was calculated using the Bland & Altman method for repeated measures. The effects of sedation (baseline versus 15 min) and OVH (baseline versus 24 h) were assessed using linear mixed models. Responsiveness to the administration of rescue analgesia (FGS scores before versus one hour after) was assessed using paired t-tests.

Results

Minimal bias (-0.057) and narrow limits of agreement (-0.351 to 0.237) were observed between the FGS-IMG and FGS-RT. Scores at baseline (FGS-RT: 0.16 ± 0.13 and FGS-IMG: 0.14 ± 0.13) were not different after sedation (FGS-RT: 0.2 ± 0.15, p = 0.39 and FGS-IMG: 0.16 ± 0.15, p = 0.99) nor at 24 h after extubation (FGS-RT: 0.16 ± 0.12, p = 0.99 and FGS-IMG: 0.12 ± 0.12, p = 0.96). Thirteen cats required rescue analgesia; their FGS scores were lower one hour after analgesic administration (FGS-RT: 0.21 ± 0.18 and FGS-IMG: 0.18 ± 0.17) than before (FGS-RT: 0.47 ± 0.24, p = 0.0005 and FGS-IMG: 0.45 ± 0.19, p = 0.015).

Conclusions

Real-time assessment slightly overestimates image scoring; however, with minimal clinical impact. Sedation with acepromazine-buprenorphine and ovariohysterectomy using a balanced anesthetic protocol did not influence the FGS scores. Responsiveness to analgesic administration was observed with both the FGS-RT and FGS-IMG.

Measurement of Pectoralis Minor Muscle Length in Women Diagnosed With Breast Cancer: Reliability, Validity, and Clinical Application

BACKGROUND

Decreased pectoralis minor muscle length is common after primary breast cancer treatment and can result in an abnormal position of the scapula. This position can contribute to shoulder pain and pathomechanics and can lead to problems such as impingement syndrome, rotator cuff tears, and frozen shoulder. Currently, there are limited reliable methods for measuring pectoralis minor length.

OBJECTIVE

The objective of this study was to examine the reliability and validity of measuring pectoralis minor length in women diagnosed with breast cancer.

DESIGN

This was a cross-sectional reliability and validity study.

METHODS

Bilateral pectoralis minor length (in centimeters) was assessed using a palpation meter in women (N = 29) diagnosed with breast cancer by 2 licensed physical therapists who were masked to the measures. Bilateral pectoralis minor length was also measured using a motion capture system to assess validity.

RESULTS

Intratester reliability (intraclass correlation coefficient, ICC [3,k] = 0.971; 95% confidence interval [CI] = 0.939-0.986; standard error of measurement [SEM] = 0.16 cm) and intertester reliability (ICC[3,k] = 0.915; 95% CI = 0.81-0.962; SEM = 0.31 cm) were excellent for the palpation meter on the affected side and the unaffected side (intratester reliability: ICC[3,k] = 0.951; 95% CI = 0.897-0.977; SEM = 0.19 cm; intertester reliability: ICC[3,k] = 0.945; 95% CI = 0.877-0.975; SEM = 0.22 cm). Significant correlations were found between the motion capture system and the palpation meter on the affected side (r = 0.87) and the unaffected side (r = 0.81). Bland-Altman plots between the palpation meter and the motion capture system demonstrated that all the measures fell within the limits of agreement.

LIMITATIONS

This study encountered possible errors with the accuracy of the motion capture system tracking because of the proximity of the markers and inherent volumetric restrictions.

CONCLUSIONS

The palpation meter is a reliable, valid, easily administered, and cost-effective tool for assessing pectoralis minor length in women with breast cancer.

A Review of the Use of Confidence Intervals for Bland-Altman Limits of Agreement in Optometry and Vision Science

SIGNIFICANCE

Confidence intervals are still seldom reported for Bland-Altman 95% limits of agreement. When they are reported, 50% of articles use approximate methods and 50% use exact methods.

PURPOSE

Bland-Altman limits of agreement can be unreliable estimates, especially for small sample sizes. However, authors seldom use confidence intervals for limits of agreement. This article reviews their use in Optometry and Vision Science.

METHODS

A keyword search for "Bland," "Altman," "Bland-Altman," "LoA," and "limits of agreement" was conducted on the Optometry and Vision Science website within a time range from January 2016 to December 2018.

RESULTS

Fifty articles were reported or were judged to use Bland-Altman analysis; sample sizes ranged from 3 to 2072. Eight of these article reported confidence limits for limits of agreement, four of which used exact methods and four used Bland and Altman's approximate method.

CONCLUSIONS

Use of confidence intervals for limits of agreement has increased in Optometry and Vision Science but is far from universal. To assist researchers in calculating exact confidence limits for Bland-Altman limits of agreement, spreadsheets are included for performing the calculations and generating Bland-Altman plots with the confidence intervals included.

Invasive and non-invasive point-of-care testing and point-of-care monitoring of the hemoglobin concentration in human blood - how accurate are the data?

In this review, scientific investigations of point-of-care testing (POCT) and point-of-care monitoring (POCM) devices are summarized with regard to the measurement accuracy of the hemoglobin concentration. As a common basis, information according to the Bland and Altman principle [bias, limits of agreement (LOA)] as well as the measurement accuracy and precision are considered, so that the comparability can be mapped. These collected data are subdivided according to the manufacturers, devices and procedures (invasive and non-invasive). A total of 31 devices were identified. A comparability of the scientific investigations in particular was given for 23 devices (18 invasive and five non-invasive measuring devices). In terms of measurement accuracy, there is a clear leap between invasive and non-invasive procedures, while no discernible improvement can be derived in the considered time frame from 2010 to 2018. According to the intended use, strict specifications result from the clinical standards, which are insufficiently met by the systems. More stringent requirements can be derived both in the area of blood donation and in the treatment of patients.

Femoral and tibial torsion measurements based on EOS imaging compared to 3D CT reconstruction measurements

Background

The EOS imaging system is an advanced piece of equipment for full-body imaging, but its reliability and reproducibility should be further verified.

Methods

A prospective study was conducted including 18 adult volunteers (36 lower extremities) (24±2 years old). Femoral and tibial torsion were measured by both EOS imaging and three-dimensional computed tomography (3D CT) reconstruction. Bland-Altman plots were performed to evaluate the difference between femoral and tibial torsion measurements obtained by these two methods. The intraclass correlation coefficient (ICC) was used to evaluate intrareader agreement.

Results

The mean difference between the two methods was 3° (range, -9° to 4°) for femoral torsion, 0° (range, -6° to 6°) for tibial torsion and 0° (range, -4° to 5°) for femorotibial torsion. No statistically significant difference between the measurements of the two methods was detected by Bland-Altman plots. With the exception of one measurement of femoral torsion, one measurement of tibial torsion and one measurement of femorotibial torsion, all EOS imaging measurements were within the 95% limits of agreement (the mean ± 1.96 SD). Intrareader agreement was statistically significant (P<0.001) for all measurements, with high ICCs. For EOS imaging, the ICC was 0.92 for the femoral measurement, 0.92 for the tibial measurement and 0.918 for the femorotibial measurement; the corresponding values for CT were 0.950, 0.927 and 0.889.

Conclusions

There was good agreement between EOS imaging based and 3D CT reconstruction based technique in measuring femoral, tibial and femorotibial torsion; and good reliability and reproducibility of EOS Imaging in measuring femoral, tibial and femorotibial torsion was also verified.

Comparison of blood pressure measurements in the upper and lower extremities versus arterial blood pressure readings in children under general anesthesia

Purpose

To compare invasive blood pressure (IBP) readings obtained from an arterial cannula with non-invasive blood pressure (NIBP) measurements from oscillometric cuffs on the upper and lower extremities of infants and children under general anesthesia.

Patients and methods

Patients under 10 years of age were enrolled in our study if they were to receive general anesthesia with planned placement of a radial arterial cannula. At 5 mins intervals, IBP was measured using a fluid-coupled pressure transducer and NIBP was measured with two oscillometers with appropriately sized cuffs placed on the upper arm and lower leg, for 10 readings per patient.

Results

The study enrolled 18 boys and 12 girls, ranging in age from 0 to 8 years. Across 300 data points, the absolute difference between the arm and invasive mean arterial pressure (MAP) measurements was 7±7 mmHg (range: 0–52 mmHg). The absolute difference between the leg and invasive MAP measurements was 8±8 mmHg (range: 0–52 mmHg). Although both non-invasive measurement sites demonstrated frequent deviation from invasive measurement, large deviations were more common when BP was measured at the leg (81 of 298 observations (27%) deviating by >10 mmHg) compared to the arm (60 of 300 observations (20%) deviating by >10 mmHg).

Conclusion

The frequency of clinically significant NIBP deviation in children under general anesthesia supports the importance of IBP monitoring when hemodynamic fluctuations are likely and would be particularly detrimental. NIBP measured at the lower leg is more likely to result in clinically significant deviation from invasively measured MAP than NIBP values obtained from an upper arm.

Stressing the accuracy: Wrist-worn wearable sensor validation over different conditions

Wearable sensors are promising instruments for conducting both laboratory and ambulatory research in psychophysiology. However, scholars should be aware of their measurement error and the conditions in which accuracy is achieved. This study aimed to assess the accuracy of a wearable sensor designed for research purposes, the E4 wristband (Empatica, Milan, Italy), in measuring heart rate (HR), heart rate variability (HRV), and skin conductance (SC) over five laboratory conditions widely used in stress reactivity research (seated rest, paced breathing, orthostatic, Stroop, speech task) and two ecological conditions (slow walking, keyboard typing). Forty healthy participants concurrently wore the wristband and two gold standard measurement systems (i.e., electrocardiography and finger SC sensor). The wristband accuracy was determined by evaluating the signal quality and the correlations with and the Bland-Altman plots against gold standard-derived measurements. Moreover, exploratory analyses were performed to assess predictors of measurement error. Mean HR measures showed the best accuracy over all conditions. HRV measures showed satisfactory accuracy in seated rest, paced breathing, and recovery conditions but not in dynamic conditions, including speaking. Accuracy was diminished by wrist movements, cognitive and emotional stress, nonstationarity, and larger wrist circumferences. Wrist SC measures showed neither correlation nor visual resemblance with finger SC signal, suggesting that the two sites may reflect different phenomena. Future studies are needed to assess the responsivity of wrist SC to emotional and cognitive stress. Limitations and implications for laboratory and ambulatory research are discussed.

Comparative evaluation of two immunoassays for cerebrospinal fluid β-Amyloid1-42 measurement

AIM OF THE STUDY

Beta-Amyloid 1-42 peptide (βA42) is a cerebro-spinal fluid (CSF) biomarker, key element of the NIA Alzheimer's disease diagnostic criteria. The enzyme-linked immunosorbent assay (ELISA) has been the mainstay method for βA42 measurement on cerebrospinal fluid (CSF). Recently, a new βA42 measurement method in chemiluminescence enzyme immunoassay (CLEIA) is available on Lumipulse G 600 II automatic platform. The aim of the work was to evaluate the concordance of the ELISA and the new method (CLEIA) in the CSF βA42 levels measurement.

MATERIALS AND METHODS

CSF βA42 levels were assayed in 49 samples using the ELISA method (Innotest β- amyloid 1-42, Fujirebio Europe N.V., Gent, Belgium) and CLEIA method on Lumipulse G600II fully automatic platform (Lumipulse G β- amyloid 1-42, Fujirebio Europe N.V., Gent, Belgium). We compared values of the two methods using acceptability interval based on Inherent Combined Imprecision (ICI), the Passing-Bablok regression analysis, the Pearson correlation coefficient (r) and the Bland-Altman plot.

RESULTS

The analysis of the ICI showed that the two methods differ substantially. The regression equation (y = -103.04 + 1.52×) highlighted the presence of proportional systematic difference, without significant deviation from linearity (p = .42). The Pearson correlation coefficient was 0.826. The Bland-Altman plot analysis showed a significant systematic difference in the two methods: ELISA measurements were in average -27.06% (95% CI -31.89 to -22.23%) lower compared to CLEIA ones.

CONCLUSIONS

Our study highlighted a difference between the two methods. Therefore, the cut-off for the normal levels of βA42 should be reviewed in the laboratory report.

Reproducibility of measuring QRS duration and implications for optimization of interventricular pacing delay in cardiac resynchronization therapy

BACKGROUND

QRS narrowing after CRT is a predictor of patient outcome. Further narrowing can be obtained by interventricular pacing delay (VVd) optimization, raising interest to inter and intraobserver variation in manual measurements of QRS duration.

METHODS

(a) Variation in intrinsic rhythm QRS duration in CRT patients with LBBB: In 40 intrinsic 12-lead ECGs, six observers measured QRS duration defined as widest QRS in any lead. In 20 of these ECGs, two observers repeated the measurements. (b) Variation in paced QRS duration at different VVd settings and agreement in selecting the narrowest QRS: In 20 CRT patients, five paced ECGs were recorded at different VVds. The most frequently selected VVd(s) estimated to cause the narrowest QRS in each patient defined the optimal VVd. Two observers repeated the measurements and VVd selections.

RESULTS

Absolute interobserver difference in measured QRS duration in intrinsic rhythm ECGs was mean 2 ms, range (-40; 40 ms), mean limits of agreement (LoA): -21; 25 ms. Absolute interobserver difference in measured QRS duration in paced ECGs was mean 3 ms, range (-50; 60 ms), mean LoA: -20; 27 ms. There was no difference in LoA between intrinsic and paced QRS duration (lower limit p = 0.68; upper limit p = 0.44). The optimal VVd was included in 17/20 (85%) of the VVd selections by six observers. Interobserver variation was comparable with the intraobserver variation.

CONCLUSIONS

Interobserver variation and intraobserver variation in manually measured paced and intrinsic rhythm QRS duration are clinically acceptable and comparable in a cohort of CRT patients. Inter and intraobserver reproducibility for selecting the optimal VVd is good and warrants manual VVd optimization for QRS narrowing in CRT.

Peak power output in handcycling of individuals with a chronic spinal cord injury: predictive modeling, validation and reference values

Purpose: To develop and validate predictive models for peak power output to provide guidelines for individualized handcycling graded exercise test protocols for people with spinal cord injury (SCI); and to define reference values.Materials and methods: Power output was measured in 128 handcyclists with SCI during a synchronous handcycling exercise test. Eighty percent of the data was used to develop four linear regression models: two theoretical and two statistical models with peak power output (in W and W/kg) as dependent variable. The other 20% of the data was used to determine agreement between predicted versus measured power output. Reference values were based on percentiles for the whole group.Results: Lesion level, handcycling training hours and sex or body mass index were significant determinants of peak power output. Theoretical models (R² = 42%) were superior to statistical models (R²=39% for power output in W, R² = 30% for power output in W/kg). The intraclass correlation coefficients varied between 0.35 and 0.60, depending on the model. Absolute agreement was low.Conclusions: Both models and reference values provide insight in physical capacity of people with SCI in handcycling. However, due to the large part of unexplained variance and low absolute agreement, they should be used with caution. Implications for rehabilitationIndividualization of the graded exercise test protocol is very important to attain the true peak physical capacity in individuals with spinal cord injury.The main determinants to predict peak power output during a handcycling graded exercise test for individuals with a spinal cord injury are lesion level, handcycling training hours and sex or body mass index.The predictive models for peak power output should be used with caution and should not replace a graded exercise test.

Agreement between self-/home-measured and assessor-measured waist circumference at three sites in adolescents/children

The objective of this study was to assess the validity of the self-/home-measured waist circumference (WC) method in children/adolescents at three sites: at the level of the umbilicus, immediately above the iliac crest, and at the midpoint of the lower margin of the last palpable rib and top of the iliac crest. A cross-sectional study of 3360 Hong Kong Chinese children/adolescents was conducted, with 2980 (88.7%) participants included in the final analysis. The WC of children aged 6 to 9 was measured at the three sites by their parent/guardian at home followed by measurement by trained assessors at school within one week. Children/adolescents between the ages of 10 and 17 self-measured their WC at the three sites during school hours, followed by measurements by the trained assessors. Bland-Altman limits of agreement (LOA) analysis was performed to evaluate between-measurement agreement. The difference between assessor- and self-/home-measured WC was defined as ≤ ±2.5 cm for the upper and lower LOA at all three sites as an a priori criterion based on the assessor-measured inter-rater results. The results showed that most measurements (about 96%) at each site was within 95% of the LOA. Of the three measurement sites, the smallest LOA interval width was found at the umbilicus site, with an upper LOA of 5.08 and 7.13 and lower LOA of -2.61 and -3.43 in boys and girls, respectively. In conclusion, the range of LOA was relatively large, exceeding the acceptable limits of the predefined a priori criterion of upper and lower LOA, and thus suggesting disagreement between the two measurement methods. The use of WC as a measure of abdominal obesity in clinical practice/epidemiological studies should be restricted to measurement by trained health professionals/research staff.

1 H-MRS for the assessment of renal triglyceride content in humans at 3T: A primer and reproducibility study

BACKGROUND

Renal steatosis (fatty kidney) is a potential biomarker for obesity-related renal disease; however, noninvasive assessment of renal fat content remains a technical challenge.

PURPOSE

To evaluate reproducibility and explore clinical application of renal metabolic imaging for the quantification of renal triglyceride content (TG) using proton magnetic resonance spectroscopy (¹ H-MRS).

STUDY TYPE

Reproducibility and clinical cohort study.

POPULATION

Twenty-three healthy volunteers (mean age 30.1 ± 13.4 years) and 15 patients with type 2 diabetes mellitus (T2DM) (mean age 59.3 ± 7.0 years).

FIELD STRENGTH/SEQUENCE

3T, single-voxel point resolved spectroscopy (PRESS).

ASSESSMENT

Intra- and interexamination reproducibility of renal TG was assessed in healthy volunteers, and compared to T2DM patients. Intraexamination differences were obtained by repeating the ¹ H-MRS measurement directly after the first ¹ H-MRS without repositioning of the subject or changing surface coil and measurement volumes. Interexamination variability was studied by repeating the scan protocol after removal and replacement of the subject in the magnet, and subsequent repositioning of body coil and measurement volumes.

STATISTICAL TESTS

Reproducibility was determined using Pearson's correlation and Bland-Altman analyses. Differences in TG% between healthy volunteers and T2DM patients were assessed using the Mann-Whitney U-test.

RESULTS

After logarithmic (log) transformation, both intraexamination (r = 0.91, n = 19) and interexamination (r = 0.73, n = 9) measurements of renal TG content were highly correlated with the first renal TG measurements. Intraexamination and interexamination limits of agreement of renal log TG% were respectively [-1.36%, + 0.84%] and [-0.77%, + 0.62%]. Backtransformed limits of agreement were [-0.89%,+0.57%] and [-0.55%, + 0.43%] multiplied by mean TG for intra- and interexamination measurements. Overall median renal TG content was 0.12% [0.08, 0.22; 25th percentile, 75th percentile] in healthy volunteers and 0.20% [0.13, 0.22] in T2DM patients (P = 0.08).

DATA CONCLUSION

Renal metabolic imaging using 3T ¹ H-MRS is a reproducible technique for the assessment of renal triglyceride content.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2018;48:507-513.

Concordance and Reliability of Photogrammetric Protocols for Measuring the Cervical Lordosis Angle: A Systematic Review of the Literature

OBJECTIVE

The aim of this study was to examine and interpret the concordance, accuracy, and reliability of photogrammetric protocols available in the literature for evaluating cervical lordosis in an adult population aged 18 to 59 years.

METHODS

A systematic search of 6 electronic databases (MEDLINE via PubMed, LILACS, CINAHL, Scopus, ScienceDirect, and Web of Science) located studies that assessed the reliability and/or concordance and/or accuracy of photogrammetric protocols for evaluating cervical lordosis, compared with radiography. Articles published through April 2016 were selected. Two independent reviewers used a critical appraisal tool (QUADAS and QAREL) to assess the quality of the selected studies.

RESULTS

Two studies were included in the review and had high levels of reliability (intraclass correlation coefficient: 0.974-0.98). Only 1 study assessed the concordance between the methods, which was calculated using Pearson's correlation coefficient. To date, the accuracy of photogrammetry has not been investigated thoroughly.

CONCLUSION

We encountered no study in the literature that investigated the accuracy of photogrammetry in diagnosing hyperlordosis of cervical spine. However, both current studies report high levels of intra- and interrater reliability. To increase the level of evidence of photogrammetry in the evaluation of cervical lordosis, it is necessary to conduct further studies using a larger sample to increase the external validity of the findings.

The quality of working life questionnaire for cancer survivors (QWLQ-CS): factorial structure, internal consistency, construct validity and reproducibility

Background

To assess the factorial structure, internal consistency, construct validity and reproducibility of the Quality of Working Life Questionnaire for Cancer Survivors (QWLQ-CS).

Methods

An Exploratory Factor Analysis (EFA) was performed on QWLQ-CS data from a sample of employed cancer survivors to establish the final number of items and factorial structure of the QWLQ-CS. Internal consistency was assessed using Cronbach’s alpha. In a second sample of (self-)employed cancer survivors, construct validity was tested by convergent validity (correlations of QWLQ-CS with construct-related questionnaires), and discriminative validity (difference in QWLQ-CS scores between cancer survivors and employed people without cancer). In a subgroup of stable cancer survivors subtracted from the second sample, reproducibility was evaluated by Intraclass Correlation Coefficient (ICC) and Standard Error of Measurement (SEM).

Results

EFA on QWLQ-CS data of 302 cancer survivors resulted in 23 items and five factors. The internal consistency of the QWLQ-CS was Cronbach’s α = 0.91. Convergent validity on data of 130 cancer survivors resulted in r = 0.61–0.70. QWLQ-CS scores of these cancer survivors statistically differed (p = 0.04) from employed people without cancer (N = 45). Reproducibility of QWLQ-CS data from 87 cancer survivors demonstrated an ICC of 0.84 and a SEM of 9.59.

Conclusions

The five-factor QWLQ-CS with 23 items and adequate internal consistency, construct validity, and reproducibility at group level can be used in clinical and occupational healthcare, and research settings.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3966-1) contains supplementary material, which is available to authorized users.

Influence of catecholamines at different dosages on the function of the LiDCO sensor in isoflurane anesthetized horses

OBJECTIVE

To compare the lithium dilution method for cardiac output (LiDCO) and bolus-thermo-dilution (BTD) measurements before and during infusion of dobutamine, dopamine, phenylephrine, or noradrenaline at 2 different doses in anesthetized horses and to examine the correlation between sensor voltages (saline-blood exposed) and possible measurement errors.

DESIGN

Prospective experimental study.

SETTING

University teaching hospital.

ANIMALS

Nine Warmblood horses.

INTERVENTIONS

Following 90 minutes of equilibration, 3 different doses of dobutamine (0.5-3 μg/kg/min), dopamine (1-5 μg/kg/min), phenylephrine (0.5-3 μg/kg/min), or noradrenaline (0.1-0.5 μg/kg/min) were administered for 15 minutes in anesthetized horses, and measurements using the LiDCO were performed at the lowest and highest doses. Pairs of LiDCO and BTD measurements were collected and sensor voltages exposed to blood and saline were measured before and at the end of each infusion period. Agreement between LiDCO and BTD was assessed with the Bland-Altman method.

MEASUREMENT AND MAIN RESULTS

The biases (2 standard deviations) before infusion of dobutamine, dopamine, phenylephrine, and noradrenaline were 1.1 (5.7), 1.6 (7.3), 0.2 (6.6), and 1.5 (4.1) L/min, respectively, and minimally and nonsignificantly changed following low-dose catecholamine infusions. Following infusion of higher doses, biases were significantly higher compared to baseline with 10.7 (7.8), 11.2 (11.9), 6.9 (11.7), and 3.5 (3.8) L/min, respectively. The difference between saline- and blood-exposed sensor voltage decreased during infusion of high doses of catecholamines with correlations (r_s = 0.62) between cardiac output differences and sensor voltage differences (saline-blood).

CONCLUSIONS

This study demonstrated that catecholamines could lead to overestimation in a dose-dependent fashion in LiDCO measurements. Monitoring changes in sensor voltage differences (saline-blood) is a valuable and clinically applicable tool to predict errors in LiDCO measurements.

Random Forest-Based Approach for Maximum Power Point Tracking of Photovoltaic Systems Operating under Actual Environmental Conditions

Many maximum power point tracking (MPPT) algorithms have been developed in recent years to maximize the produced PV energy. These algorithms are not sufficiently robust because of fast-changing environmental conditions, efficiency, accuracy at steady-state value, and dynamics of the tracking algorithm. Thus, this paper proposes a new random forest (RF) model to improve MPPT performance. The RF model has the ability to capture the nonlinear association of patterns between predictors, such as irradiance and temperature, to determine accurate maximum power point. A RF-based tracker is designed for 25 SolarTIFSTF-120P6 PV modules, with the capacity of 3 kW peak using two high-speed sensors. For this purpose, a complete PV system is modeled using 300,000 data samples and simulated using the MATLAB/SIMULINK package. The proposed RF-based MPPT is then tested under actual environmental conditions for 24 days to validate the accuracy and dynamic response. The response of the RF-based MPPT model is also compared with that of the artificial neural network and adaptive neurofuzzy inference system algorithms for further validation. The results show that the proposed MPPT technique gives significant improvement compared with that of other techniques. In addition, the RF model passes the Bland–Altman test, with more than 95 percent acceptability.

Comparing heteroscedastic measurement systems with the probability of agreement

Deciding whether two measurement systems agree well enough to be used interchangeably is important in medical and clinical contexts. Recently, the probability of agreement was proposed as an alternative to comparison techniques such as correlation, regression, and the limits of agreement approach, when the systems’ measurement errors are homoscedastic. However, in medical and clinical contexts, it is common for measurement variability to increase proportionally with the magnitude of measurement. In this article, we extend the probability of agreement analysis to accommodate heteroscedastic measurement errors, demonstrating the versatility of this simple metric. We illustrate its use with two examples: one involving the comparison of blood pressure measurement devices, and the other involving the comparison of serum cholesterol assays.

A systematic review of observational pain assessment instruments for use with nonverbal intubated critically ill adult patients in the emergency department: an assessment of their suitability and psychometric properties

AIM AND OBJECTIVE

To examine the psychometric properties and suitability of the available observational pain instruments for potential use with nonverbal critically ill adult patients in the emergency department.

BACKGROUND

In the emergency department, assessing pain in critically ill patients is challenging, especially those unable to communicate the presence of pain. Critically ill patients are commonly unable to verbally communicate pain due to altered oral communication (e.g. endotracheal intubation) and/or diminished consciousness (e.g. sedation, delirium), placing them at great risk of inadequate pain management. Over half of intensive care critically ill intubated patients experience moderate-to-severe pain whilst intubated and mechanically ventilated.

DESIGN

Systematic review.

DATA SOURCES

The CINAHL, EMBASE, MEDLINE, ProQuest databases, and the Cochrane Library and the National Institute of Clinical Excellence were also searched from their date of inception to April 2016, with no language restrictions applied.

REVIEW METHOD

Studies were identified using predetermined inclusion criteria. Data were extracted and summarised and underwent evaluation using published classification of psychometric tests for consistency of interpretation.

RESULTS

Twenty-six studies evaluating five observational pain assessment instruments that had been used with critically ill intubated patients were identified. All five instruments included behavioural indicators, with two including physiologic indicators. All five instruments have undergone validity and reliability testing involving nonverbal critically ill intubated patients, three were examined for feasibility, and one instrument underwent sensitivity and specificity testing. None have been tested within the emergency department with nonverbal critically ill intubated adult patients.

CONCLUSION

The use of an appropriate and valid observational pain assessment instrument is fundamental to detecting and optimising pain management in nonverbal critically ill intubated patients in the emergency department. Of the observational pain assessment instruments reviewed, the Critical-Care Pain Observation Tool was identified as most appropriate for testing in a prospective trial in an emergency department setting.

The UEA Small RNA Workbench: A Suite of Computational Tools for Small RNA Analysis

RNA silencing (RNA interference, RNAi) is a complex, highly conserved mechanism mediated by short, typically 20-24 nt in length, noncoding RNAs known as small RNAs (sRNAs). They act as guides for the sequence-specific transcriptional and posttranscriptional regulation of target mRNAs and play a key role in the fine-tuning of biological processes such as growth, response to stresses, or defense mechanism.High-throughput sequencing (HTS) technologies are employed to capture the expression levels of sRNA populations. The processing of the resulting big data sets facilitated the computational analysis of the sRNA patterns of variation within biological samples such as time point experiments, tissue series or various treatments. Rapid technological advances enable larger experiments, often with biological replicates leading to a vast amount of raw data. As a result, in this fast-evolving field, the existing methods for sequence characterization and prediction of interaction (regulatory) networks periodically require adapting or in extreme cases, a complete redesign to cope with the data deluge. In addition, the presence of numerous tools focused only on particular steps of HTS analysis hinders the systematic parsing of the results and their interpretation.The UEA small RNA Workbench (v1-4), described in this chapter, provides a user-friendly, modular, interactive analysis in the form of a suite of computational tools designed to process and mine sRNA datasets for interesting characteristics that can be linked back to the observed phenotypes. First, we show how to preprocess the raw sequencing output and prepare it for downstream analysis. Then we review some quality checks that can be used as a first indication of sources of variability between samples. Next we show how the Workbench can provide a comparison of the effects of different normalization approaches on the distributions of expression, enhanced methods for the identification of differentially expressed transcripts and a summary of their corresponding patterns. Finally we describe individual analysis tools such as PAREsnip, for the analysis of PARE (degradome) data or CoLIde for the identification of sRNA loci based on their expression patterns and the visualization of the results using the software. We illustrate the features of the UEA sRNA Workbench on Arabidopsis thaliana and Homo sapiens datasets.

Application of Mixed Effects Limits of Agreement in the Presence of Multiple Sources of Variability: Exemplar from the Comparison of Several Devices to Measure Respiratory Rate in COPD Patients

Introduction

The Bland-Altman limits of agreement method is widely used to assess how well the measurements produced by two raters, devices or systems agree with each other. However, mixed effects versions of the method which take into account multiple sources of variability are less well described in the literature. We address the practical challenges of applying mixed effects limits of agreement to the comparison of several devices to measure respiratory rate in patients with chronic obstructive pulmonary disease (COPD).

Methods

Respiratory rate was measured in 21 people with a range of severity of COPD. Participants were asked to perform eleven different activities representative of daily life during a laboratory-based standardised protocol of 57 minutes. A mixed effects limits of agreement method was used to assess the agreement of five commercially available monitors (Camera, Photoplethysmography (PPG), Impedance, Accelerometer, and Chest-band) with the current gold standard device for measuring respiratory rate.

Results

Results produced using mixed effects limits of agreement were compared to results from a fixed effects method based on analysis of variance (ANOVA) and were found to be similar. The Accelerometer and Chest-band devices produced the narrowest limits of agreement (-8.63 to 4.27 and -9.99 to 6.80 respectively) with mean bias -2.18 and -1.60 breaths per minute. These devices also had the lowest within-participant and overall standard deviations (3.23 and 3.29 for Accelerometer and 4.17 and 4.28 for Chest-band respectively).

Conclusions

The mixed effects limits of agreement analysis enabled us to answer the question of which devices showed the strongest agreement with the gold standard device with respect to measuring respiratory rates. In particular, the estimated within-participant and overall standard deviations of the differences, which are easily obtainable from the mixed effects model results, gave a clear indication that the Accelerometer and Chest-band devices performed best.

Confidence and coverage for Bland-Altman limits of agreement and their approximate confidence intervals

Bland and Altman described approximate methods in 1986 and 1999 for calculating confidence limits for their 95% limits of agreement, approximations which assume large subject numbers. In this paper, these approximations are compared with exact confidence intervals calculated using two-sided tolerance intervals for a normal distribution. The approximations are compared in terms of the tolerance factors themselves but also in terms of the exact confidence limits and the exact limits of agreement coverage corresponding to the approximate confidence interval methods. Using similar methods the 50th percentile of the tolerance interval are compared with the k values of 1.96 and 2, which Bland and Altman used to define limits of agreements (i.e. [Formula: see text]+/- 1.96S_d and [Formula: see text]+/- 2S_d). For limits of agreement outer confidence intervals, Bland and Altman's approximations are too permissive for sample sizes <40 (1999 approximation) and <76 (1986 approximation). For inner confidence limits the approximations are poorer, being permissive for sample sizes of <490 (1986 approximation) and all practical sample sizes (1999 approximation). Exact confidence intervals for 95% limits of agreements, based on two-sided tolerance factors, can be calculated easily based on tables and should be used in preference to the approximate methods, especially for small sample sizes.