Point of care ultrasound combined with CTS-6 to diagnose idiopathic carpal tunnel syndrome

BACKGROUND

This study aimed to demonstrate the effectiveness of our new diagnostic chart using point of care ultrasound combined with CTS-6 for diagnosing idiopathic carpal tunnel syndrome.

METHODS

We conducted a retrospective analysis of the data of patients who visited our department and received point of care ultrasound combined with CTS-6 from 2020 to 2023. Data regarding age, sex, initial and final diagnosis, cross-sectional area of the median nerve, CTS-6 score, and electrodiagnostic severity were obtained and statistically analyzed.

RESULTS

Of the 177 wrists included in our study, 138 (78 %) were diagnosed with carpal tunnel syndrome, while 39 (22 %) were not (non-carpal tunnel syndrome). With our diagnostic method, 127 wrists (72 %) were diagnosed initially with carpal tunnel syndrome, 23 wrists (13 %) with non-carpal tunnel syndrome, and the rest 27 wrists (15 %) as borderline. Our initial diagnoses of carpal tunnel syndrome and non-carpal tunnel syndrome were maintained in all cases except for two. Cross-sectional area, CTS-6 score, and electrodiagnostic severity showed a positive correlation. A post hoc analysis showed that the new scoring system (CTS-6 score + 2 × cross-sectional area) with a cutoff value of 31.25 points showed a sensitivity as high as 95 % and a specificity of 100 %.

CONCLUSIONS

Our findings suggest that most suspected idiopathic carpal tunnel syndrome cases can be diagnosed correctly using the diagnostic chart. Although additional tools, including electrodiagnostic studies, may be needed for borderline cases, the use of point of care ultrasound combined with CTS-6 may be a recommendable first-line confirmatory test because point of care ultrasound and CTS-6 could be complementary tools, and this chart may be especially beneficial for atypical or outlier cases.

LEVEL OF EVIDENCE

Diagnostic III.

Significance of carcinoembryonic antigen detection in the early diagnosis of colorectal cancer: A systematic review and meta-analysis

BACKGROUND

Colorectal cancer (CRC) is a prevalent malignant tumor involving adenomas that develop into malignant lesions. Carcinoembryonic antigen (CEA) is a non-specific serum biomarker upregulated in CRC. The concentration of CEA is modulated by tumor stage and grade, tumor site in the colon, ploidy status, and patient smoking status. This study aimed to evaluate current evidence regarding the diagnostic power of CEA levels in the early detection of CRC recurrence in adults.

AIM

To evaluate current evidence regarding the diagnostic power of CEA levels in the early detection of CRC recurrence in adults.

METHODS

A systematic search was performed using four databases: MEDLINE, Cochrane Trials, EMBASE, and the Web of Science. The inclusion criteria were as follows: Adult patients aged ≥ 18 years who had completed CRC curative treatment and were followed up postoperatively; reporting the number of CRC recurrences as an outcome; and randomized, clinical, cohort, and case-control study designs. Studies that were not published in English and animal studies were excluded. The following data were extracted by three independent reviewers: Study design, index tests, follow-up, patient characteristics, and primary outcomes. All statistical analyses were performed using the RevMan 5.4.1.

RESULTS

A total of 3232 studies were identified, with 73 remaining following the elimination of duplicates. After screening on predetermined criteria, 12 studies were included in the final analysis. At a reference standard of 5 mg/L, CEA detected only approximately half of recurrent CRCs, with a pooled sensitivity of 59% (range, 33%-83%) and sensitivity of 89% (range, 58%-97%).

CONCLUSION

CEA is a significant marker for CRC diagnosis. However, it has insufficient sensitivity and specificity to be used as a single biomarker of early CRC recurrence, with an essential proportion of false negatives.

Aspergillus-specific IgG antibodies for diagnosing chronic pulmonary aspergillosis compared to the reference standard

OBJECTIVES

To evaluate the performance of Aspergillus-specific IgG antibodies for diagnosing chronic pulmonary aspergillosis (CPA) by using a cohort of patients with histologically proven CPA as a reference standard.

METHODS

We collected Aspergillus-specific IgG antibody titres from patients with histologically proven CPA in collaboration with CPAnet study sites in Denmark, Germany, Belgium, India, Moldova, and Pakistan (N = 47). Additionally, sera from diseased and healthy controls were prospectively collected at the Medical Clinic of the Research Center, Borstel, Germany (n = 303). Aspergillus-specific IgG antibody titres were measured by the ImmunoCAP® assay (Phadia 100, Thermo Fisher Scientific, Uppsala, Sweden). An Aspergillus-specific IgG antibody titre ≥50 mgA/L was considered positive.

RESULTS

Using patients with histologically proven CPA as the reference standard, the ImmunoCAP® Aspergillus-specific IgG antibody test had a sensitivity and specificity of 85.1% (95% CI: 71.7-93.8%) and 83.6% (95% CI: 78.0-88.3%), respectively. Patients with histologically proven CPA had significantly higher Aspergillus-specific IgG antibody titre with a median of 83.45 mgA/L (interquartile range 38.9-115.5) than all other cohorts (p < 0.001). False-positive test results occurred in one-third of 79 healthy controls.

DISCUSSION

Our study results confirm a high sensitivity of the Aspergillus-specific IgG antibody test for the diagnosis of CPA when using patients with histologically proven CPA as a reference standard. However, positive test results should always match radiological findings as false-positive test results limit the interpretation of the test.

Gamma camera-specific reference standards for radioactive iodine uptake measurements

BACKGROUND

Current guidelines of the radioiodine uptake (RAIU) test allow the use of different equipment, isotopes, activity and region-of-interest (ROI). We evaluated presence and extent of these differences in clinical practice and evaluated the effect of some of these variations on RAIU outcomes. Also, gamma camera-specific reference standards were calculated and retrospectively compared with measurements obtained during clinical RAIU tests.

MATERIALS AND METHODS

First, questionnaires were sent to Dutch nuclear medicine departments requesting information about equipment usage, isotope, isotope formulation, activity and measurement techniques. Secondly, a neck phantom containing a range of activities in capsule or water-dissolved formulation was scanned. Counts were measured using automatic ROI, square box ROI or all counts in the image. Thirdly, clinical RAIU data were collected during 2015-2018 using three different gamma cameras. Reference standards for each scanner were calculated using regression analysis between reference activity and measured counts. Uptake measurements using this gamma camera-specific reference standard were compared with original measurements.

RESULTS

The survey demonstrated significant differences in isotope, isotope formulation, activity, use of neck phantoms, frequency and duration of reference measurements, distance to collimator, use of background measurements and ROI delineation. The phantom study demonstrated higher counts for the water-dissolved formulation than capsules using both automatic and square box ROI. Also, higher counts were found using a square box ROI than an automatic ROI. The retrospective study showed feasibility of RAIU calculations using camera-specific reference standards and good correlation with the original RAIU measurements.

CONCLUSIONS

This study demonstrated considerable technical variation in RAIU measurement in clinical practice. The phantom study demonstrated that these differences could result in differences in count measurements, potentially resulting in different dose calculations for radioactive iodine therapy. Retrospective data suggest that camera-specific reference standards may be used instead of individual reference measurements using separate activity sources, which may thus eliminate some sources of variation.

Influence of Electrodiagnostic Studies on Surgery for Carpal Tunnel Syndrome: A Retrospective Analysis of Data from a Single Urban Institution

Background: This study aimed to clarify the influence of preoperative electrodiagnostic (EDX) utilisation and its severity on surgically treated patients with carpal tunnel syndrome (CTS). Methods: This retrospective study analysed the data of patients who underwent CTS surgery at our facility from 2012 to 2022. Data regarding age, sex, affected side, diabetes mellitus, rheumatoid arthritis, haemodialysis and insurance type were collected, along with the following clinical information: utilisation of EDX, steroid injection, number of items of preoperative physical examination and history taking, intervals between symptom onset and the initial visit and between the initial visit and surgery, type of surgical procedure and surgery categorisation (primary or revision). EDX data (EDX severity, interval between EDX and surgery and concomitant nerve lesions) were also investigated. Univariate and multivariate analyses were conducted to assess the influence of EDX utilisation and severity on clinical parameters. Results: Of the 343 hands enrolled in our study, 304 (89%) underwent preoperative EDX assessment. EDX severity was classified as normal, mild, moderate or severe in 6 (2%), 18 (6%), 102 (34%) and 178 hands (58%), respectively. After the univariate and multivariable analyses, more items of preoperative physical examination and history taking were associated with non-EDX utilisation, whereas younger age, female sex and steroid injection were associated with milder EDX. Conclusions: Increased number of items of preoperative physical examination and history taking or steroid injection were independently associated with non-EDX utilisation or milder EDX, respectively, suggesting that when thorough clinical evaluation is conducted, hand surgeons may be less likely to request for EDX before surgery. Moreover, their treatment recommendation may be influenced by EDX severity. Level of Evidence: Level III (Diagnostic).

Collaborative Study to Establish National Reference Standards for Anti-HIV-1 Antibody

Background

National reference standards for anti-HIV-1 antibody are needed to evaluate the performance and maintain the quality control of anti-HIV-1 antibody assays. The aim of this study was to prepare a mixed-titer performance panel and assess its suitability as a national reference standard for anti-HIV-1 antibody according to stability, collaboration, and other studies.

Methods

Nineteen serum samples from different HIV patients were obtained, along with 15 units of fresh frozen plasma samples with negative anti-HIV-1 antibody results. Ten anti-HIV-1 antibody-positive candidate standards and two negative candidate standards were prepared based on the reactivity in the Alinity i HIV Ag/Ab combo assay (Abbott Laboratories, Wiesbaden, Germany). A collaborative study was conducted across eight laboratories using five anti-HIV-1 antibody assays. Real-time and accelerated stability were evaluated to assess the long-term stability.

Results

In the collaborative study, results of all five anti-HIV-1 antibody assays were positive for all 10 candidate standards prepared using HIV patient samples. The CV of each assay for every candidate standard was within 10%, except for one assay result. No real-time and accelerated stability change trend was observed at -70°C or -20°C, supporting that the reference standards were maintained in a stable state at -70°C for long-term storage.

Conclusions

The overall results suggest that the 12 candidate standards could serve as national reference standards for anti-HIV-1 antibody.

Low back pain of disc, sacroiliac joint, or facet joint origin: a diagnostic accuracy systematic review

Background

The accuracy of diagnostic tests available in primary care to identify the disc, sacroiliac joint, and facet joint as the source of low back pain is uncertain.

Methods

Systematic review of diagnostic tests available in primary care. MEDLINE, CINAHL, and EMBASE were searched between March 2006 and 25th January 2023. Pairs of reviewers independently screened all studies, extracted data, and assessed risk of bias using QUADAS-2. Pooling was performed for homogenous studies. Positive likelihood ratios (+LR) ≥2 and negative likelihood ratios (-LR) ≤0.5 were considered informative. This review is registered with PROSPERO (CRD42020169828).

Findings

We included 62 studies: 35 investigated the disc, 14 the facet joint, 11 the sacroiliac joint, and 2 investigated all three structures in patients with persistent low back pain. For risk of bias, the domain 'reference standard' scored worst, however approximately half the studies were of low risk of bias for every other domain. For the disc, pooling demonstrated MRI findings of disc degeneration and annular fissure resulted in informative +LRs: 2.53 (95% CI: 1.57-4.07) and 2.88 (95% CI: 2.02-4.10) and -LRs: 0.15 (95% CI: 0.09-0.24) and 0.24 (95% CI: 0.10-0.55) respectively. Pooled results for Modic type 1, Modic type 2, and HIZ on MRI, and centralisation phenomenon yielded informative +LRs: 10.00 (95% CI: 4.20-23.82), 8.03 (95% CI: 3.23-19.97), 3.10 (95% CI: 2.27-4.25), and 3.06 (95% CI: 1.44-6.50) respectively, but uninformative -LRs: 0.84 (95% CI: 0.74-0.96), 0.88 (95% CI: 0.80-0.96), 0.61 (95% CI: 0.48-0.77), and 0.66 (95% CI: 0.52-0.84) respectively. For the facet joint, pooling demonstrated facet joint uptake on SPECT resulted in informative +LRs: 2.80 (95% CI: 1.82-4.31) and -LRs: 0.44 (95% CI: 0.25-0.77). For the sacroiliac joint, a combination of pain provocation tests and absence of midline low back pain resulted in informative +LRs of 2.41 (95% CI: 1.89-3.07) and 2.44 (95% CI: 1.50-3.98) and -LRs of 0.35 (95% CI: 0.12-1.01) and 0.31 (95% CI: 0.21-0.47) respectively. Radionuclide imaging yielded an informative +LR 7.33 (95% CI: 1.42-37.80) but an uninformative -LR 0.74 (95% CI: 0.41-1.34).

Interpretation

There are informative diagnostic tests for the disc, sacroiliac joint, and facet joint (only one test). The evidence suggests a diagnosis may be possible for some patients with low back pain, potentially guiding targeted and specific treatment approaches.

Funding

There was no funding for this study.

Development of outcomes for evaluating emergency care triage: a Delphi approach

BACKGROUND

Triage is used as standard of care for prioritization and identification of time-critical patients in the emergency department (ED) globally, but it is unclear what outcomes should be used to evaluate triage. Currently used outcomes do not include important time-critical diagnoses and conditions.

METHOD

We used 18 Swedish triage experts to collect and assess outcomes for the evaluation of 5-level triage systems. The experts suggested 68 outcomes which were then tested through a modified Delphi approach in three rounds. The outcomes aimed to identify correctly prioritized red patients (in need of a resuscitation team), and orange patients (other time critical conditions). Consensus was pre-defined as 70% dichotomized (positive/negative) concordance.

RESULTS

Diagnoses, interventions, mortality, level of care and lab results were included in the outcomes. Positive consensus was reached for 49 outcomes and negative consensus for 7 outcomes, with an 83% response rate. The five most approved outcomes were the interventions Percutaneous coronary intervention, Surgical airway and Massive transfusion together with the diagnoses Tension pneumothorax and Intracerebral hemorrhage that received specific interventions. The outcomes with the clearest disapproval included Admittance to a ward, Treatment with antihistamines and The ordering of a head computed tomography scan. The outcomes were considered valid only if occurring in or from the ED.

CONCLUSION

This study proposes a standard of 49 outcomes divided into two sets tied to red and orange priority respectively, to be used when evaluating 5-level priority triage systems; Lund Outcome Set for Evaluation of Triage (LOSET). The proposed outcomes include diagnoses, interventions and laboratory results. Before widespread implementation of LOSET, prospective testing is needed, preferably at multiple sites.

Effects of Expert-Determined Reference Standards in Evaluating the Diagnostic Performance of a Deep Learning Model: A Malignant Lung Nodule Detection Task on Chest Radiographs

OBJECTIVE

Little is known about the effects of using different expert-determined reference standards when evaluating the performance of deep learning-based automatic detection (DLAD) models and their added value to radiologists. We assessed the concordance of expert-determined standards with a clinical gold standard (herein, pathological confirmation) and the effects of different expert-determined reference standards on the estimates of radiologists' diagnostic performance to detect malignant pulmonary nodules on chest radiographs with and without the assistance of a DLAD model.

MATERIALS AND METHODS

This study included chest radiographs from 50 patients with pathologically proven lung cancer and 50 controls. Five expert-determined standards were constructed using the interpretations of 10 experts: individual judgment by the most experienced expert, majority vote, consensus judgments of two and three experts, and a latent class analysis (LCA) model. In separate reader tests, additional 10 radiologists independently interpreted the radiographs and then assisted with the DLAD model. Their diagnostic performance was estimated using the clinical gold standard and various expert-determined standards as the reference standard, and the results were compared using the t test with Bonferroni correction.

RESULTS

The LCA model (sensitivity, 72.6%; specificity, 100%) was most similar to the clinical gold standard. When expert-determined standards were used, the sensitivities of radiologists and DLAD model alone were overestimated, and their specificities were underestimated (all p-values < 0.05). DLAD assistance diminished the overestimation of sensitivity but exaggerated the underestimation of specificity (all p-values < 0.001). The DLAD model improved sensitivity and specificity to a greater extent when using the clinical gold standard than when using the expert-determined standards (all p-values < 0.001), except for sensitivity with the LCA model (p = 0.094).

CONCLUSION

The LCA model was most similar to the clinical gold standard for malignant pulmonary nodule detection on chest radiographs. Expert-determined standards caused bias in measuring the diagnostic performance of the artificial intelligence model.

Developing a reference standard for pertussis by applying a stratified sampling strategy to electronic medical record data

PURPOSE

Pertussis surveillance remains essential in Canada, but ascertainment bias limits the accuracy of surveillance data. Introducing other sources to improve detection has highlighted the importance of validation. However, challenges arise due to low prevalence, and oversampling suspected cases can introduce partial verification bias. The aim of this study was to build a reference standard for pertussis validation studies that provides adequate analytic precision and minimizes bias.

METHODS

We used a stratified strategy to sample the reference standard from a primary care electronic medical record cohort. We incorporated abstractor notes into definite, possible, ruled-out, and no mention of pertussis classifications which were based on surveillance case definitions.

RESULTS

We abstracted eight hundred records from the cohort of 404,922. There were 208 (26%) definite and 261 (32.6%) possible prevalent pertussis cases. Classifications demonstrated a wide variety of case severities. Abstraction reliability was moderate to substantial based on Cohen's kappa and raw percent agreement.

CONCLUSIONS

When conducting validation studies for pertussis and other low prevalence diseases, this stratified sampling strategy can be used to develop a reference standard using limited resources. This approach mitigates verification and spectrum bias while providing sufficient precision and incorporating a range of case severities.

Reference percentiles for bioimpedance body composition parameters of healthy individuals: A cross-sectional study

OBJECTIVES

The aim of this study was to estimate the percentage distribution of body composition parameters for healthy people at different ages from the assessment of electrical bioimpedance.

METHODS

A cross-sectional study of healthy Brazilian aged 5 years and older. Were evaluated: total body fat; percent body fat; fat-free mass; percent lean mass; fat mass index; and fat-free mass index.

RESULTS

Of 1240 participants, with a median age of 27.0 years, 52.5% were female, and 73.7% were Caucasian. Most of the body composition variables were associated with age. The fat-free mass increased from youth to adult and decreased in the elderly in both sexes, with higher values in males than in females. In males, the percentage of lean mass has higher values in adolescence compared to childhood, and in adults compared to the elderly, when analyzed from the 50^th percentile. In women, fat-free mass compared to adulthood, values were higher in childhood and lower in older ages.

CONCLUSIONS

The study is the first to describe the Brazilian reference values for most clinical parameters of bioimpedance in percentiles stratified by different life cycles and sex. These findings can be very useful in clinical practice for health promotion and monitoring the nutritional status of the individual.

Diagnostic value of chest computed tomography imaging for COVID-19 based on reverse transcription-polymerase chain reaction: a meta-analysis

Background

The computed tomography (CT) diagnostic value of COVID-19 is controversial. We summarized the value of chest CT in the diagnosis of COVID-19 through a meta-analysis based on the reference standard.

Methods

All Chinese and English studies related to the diagnostic value of CT for COVID-19 across multiple publication platforms, was searched for and collected. Studies quality evaluation and plotting the risk of bias were estimated. A heterogeneity test and meta-analysis, including plotting sensitivity (Sen), specificity (Spe) forest plots, pooled positive likelihood ratio (+LR), negative likelihood ratio (-LR), dignostic odds ratio (DOR) values and 95% confidence interval (CI), were estimated. If there was a threshold effect, summary receiver operating characteristic curves (SROC) was further plotted. Pooled area under the receiver operating characteristic curve (AUROC) and 95% CI were also calculated.

Results

Twenty diagnostic studies that represented a total of 9004 patients were included from 20 pieces of literatures after assessing all the aggregated studies. The reason for heterogeneity was caused by the threshold effect, so the AUROC = 0.91 (95% CI: 0.89–0.94) for chest CT of COVID-19. Pooled sensitivity, specificity, +LR, -LR from 20 studies were 0.91 (95% CI: 0.88–0.94), 0.71 (95% CI: 0.59–0.80), 3.1(95% CI: 2.2–4.4), 0.12 (95% CI: 0.09–0.17), separately. The I² was 85.6% (P = 0.001) by Q-test.

Conclusions

The results of this study showed that CT diagnosis of COVID-19 was close to the reference standard. The diagnostic value of chest CT may be further enhanced if there is a unified COVID-19 diagnostic standard. However, please pay attention to rational use of CT.

Graphic Abstract

STAndard Reporting of CAries Detection and Diagnostic Studies (STARCARDDS)

Aim

The aim of this paper is to present recommendations from an international workshop which evaluated the methodology and reporting of caries diagnostic studies. As a unique feature, this type of studies is focused on caries lesion detection and assessment, and many of them are carried out in vitro, because of the possibility of histological validation of the whole caries spectrum. This feature is not well covered in the existing reporting STARD guideline within the EQUATOR Network.

Participants and methods

An international working group of 13 cariology researchers was formed. The STARD checklist was reviewed and modified for caries detection and diagnosis purposes, in a three-step process of evaluation, consensual modification, and delivery during three 2-day workshops over 18 months. Special attention was paid to reporting requirements of caries studies that solely focus on reliability.

Results

The STARD checklist was modified in 14/30 items, with an emphasis on issues of sample selection (tooth selection in in vitro studies), blinding, and detailed reporting of results.

Conclusion

Following STARCARDDS (STAndard Reporting of CAries Detection and Diagnostic Studies) is expected to result in complete reporting of study design and methodology in future caries diagnosis and detection experiments both in vivo and in vitro, thus allowing for better comparability of studies and higher quality of systematic reviews.

Clinical relevance

Standardization of caries diagnostic studies leads to a better comparability among future studies, both in vivo and in vitro.

Case Study 2: Practical Analytical Considerations for Conducting In Vitro Enzyme Kinetic Studies

Characterization of enzyme kinetics in an experiment is dependent on measurement of a change in concentration of either the substrate (loss of parent) or the product (formation of metabolite). Modern analytical techniques such as ultrahigh pressure liquid chromatography, high resolution mass spectrometry, etc. have allowed accurate characterization of minute changes in concentration. Therefore, complex kinetic data such as a sigmoidal phase at low substrate concentrations or terminal half-life in a PK curve can be evaluated by stretching the limits of analytical quantification. This chapter presents some elementary dos and don'ts and provides insight into some of the underlying principles for utilizing the best possible analytical techniques when investigating enzyme kinetics. The objective of this case study is to answer the following questions: (a) Why is it necessary to determine lower and upper limits of quantification (LLOQ and ULOQ, respectively) of a bioanalytical assay, specifically for enzyme kinetic assays? How do you utilize LLOQ and ULOQ to correctly interpret your kinetic data? (b) Why should one use a linear fit and not a quadratic fit for standard curves? (c) Is quantification of an analyte possible without a reference standard? Can one assume equal signal intensities regardless of analytical technique (MS, UV)? (d) In the absence of reference standards, can you still determine kinetic constants? (e) With the need to keep substrate depletion at less than 20% for linearity assumptions, does bioanalytical variability matter? (f) What buffer do you use for your enzyme systems? How do you choose your buffer ? Does choice of bioanalytical methods (LC, MS) dictate your choice of buffer ?

Diagnostic test validation studies when there is a perfect reference standard

Before tools became available to consider diagnostic test validation studies where a 'gold-standard' is not available, new diagnostic tests were compared to a reference standard assumed to be highly accurate if not perfect. This paper reviews such 'traditional' situations with examples and methods of study design and analysis. Three situations are described, two where a perfect reference is available for either positive or negative animals, and one where the reference is perfect for both. Thus, here the authors review circumstances to be considered when validating a diagnostic test with a credible reference standard. An appropriate study design requires an unbiased selection of animals from the population to which a new test will be applied. Examples for calculating sample size and data analysis are provided. Finally, the authors discuss situations where it may be appropriate to include influential variables ('covariates') in a diagnostic test validation study..

Variabilities in Reference Standard by Radiologists and Performance Assessment in Detection of Pulmonary Embolism in CT Pulmonary Angiography

Annotating lesion locations by radiologists' manual marking is a key step to provide reference standard for the training and testing of a computer-aided detection system by supervised machine learning. Inter-reader variability is not uncommon in readings even by expert radiologists. This study evaluated the variability of the radiologist-identified pulmonary emboli (PEs) to demonstrate the importance of improving the reliability of the reference standard by a multi-step process for performance evaluation. In an initial reading of 40 CTPA PE cases, two experienced thoracic radiologists independently marked the PE locations. For markings from the two radiologists that did not agree, each radiologist re-read the cases independently to assess the discordant markings. Finally, for markings that still disagreed after the second reading, the two radiologists read together to reach a consensus. The variability of radiologists was evaluated by analyzing the agreement between two radiologists. For the 40 cases, 475 and 514 PEs were identified by radiologists R1 and R2 in the initial independent readings, respectively. For a total of 545 marks by the two radiologists, 81.5% (444/545) of the marks agreed but 101 marks in 36 cases differed. After consensus, 65 (64.4%) and 36 (35.6%) of the 101 marks were determined to be true PEs and false positives (FPs), respectively. Of these, 48 and 17 were false negatives (FNs) and 14 and 22 were FPs by R1 and R2, respectively. Our study demonstrated that there is substantial variability in reference standards provided by radiologists, which impacts the performance assessment of a lesion detection system. Combination of multiple radiologists' readings and consensus is needed to improve the reliability of a reference standard.

Effect of a formalin-based fixation method on bone mineral content in human ex-vivo specimens

OBJECTIVE

Histopathology of formalin-fixated human ex-vivo specimens may be used as reference standard for evaluation of diagnostic index tests like CBCT or MRI. The aim was to estimate changes in bone mineral content (BMC) over time in human ex-vivo bone specimens fixated in a formalin-based solution for 24 h followed by storage in an alcohol-based medium for six months, assessed by dual-energy X-ray absorptiometry (DXA).

METHODOLOGY

Bone specimens (n = 19) from human ex-vivo mandibles donated for science were included. BMC was measured by DXA before fixation (D₀), after 24 h of immersion fixation in a formalin-based solution (D₁), and hereafter every 30 days (M₁-M₆) during storage in a 30% ethanol-based storage medium for 6 months. Changes in BMC from D₀ to D₁ and from D₀ to M₆ were calculated and mean change in BMC estimated.

RESULTS

Mean change in BMC from D₀ to D₁ was -0.73% (95% CI -1.75%; 0.29%), and from D₀ to M₆ -1.19% (95% CI -2.14%; -0.23%).

CONCLUSIONS

No changes in BMC of ex-vivo human bone specimens were found after 24 h formalin-based immersion fixation. After six months storage in an ethanol-based medium, BMC mean loss of 1% was detected. In this range, changes in BMC are not clinically relevant.

Detection of mutations in the rpoB gene of rifampicin-resistant Mycobacterium tuberculosis strains inhibiting wild type probe hybridization in the MTBDR plus assay by DNA sequencing directly from clinical specimens

Background

The potential of genetic testing for rapid and accurate diagnosis of drug-resistant Mycobacterium tuberculosis strains is vital for efficient treatment and reduction in dissemination. MTBDR plus assays rapidly detect mutations related to drug resistance and wild type sequences allied with susceptibility. Although these methods are promising, the examination of molecular level performance is essential for improved assay result interpretation and continued diagnostic development. Therefore this study aimed to determine novel mutations that were inhibiting wild type probe hybridization in the Line probe assay by DNA sequencing. Using data collected from Line Probe assay (GenoType MTBDRplus assay) the contribution of absent wild type probe hybridization to the detection of rifampicin resistance was assessed via comparison to a reference standard method i.e. DNA sequencing.

Results

Sequence analysis of the rpoB gene of 47 MTB resistant strains from clinical specimens showed that 37 had a single mutation, 9 had double mutations and one had triple mutations in the ropB gene.

Conclusions

The absence of wild type probe hybridization without mutation probe hybridization was mainly the result of the failure of mutation probe hybridization and the result of the novel or rare mutations. Additional probes are necessary to be included in the Line probe assay to improve the detection of rifampicin-resistant Mycobacterium tuberculosis strains.

Potency assignment of biotherapeutic reference standards

The role of biotherapeutic proteins in the prevention and treatment of diseases such as cancers, infectious diseases, and autoimmune disorders continues to grow. The biological activity or "potency" of a biotherapeutic reflects its mechanism of action and thus its efficacy. The potency of these complex biomolecules cannot be quantitatively correlated to chemical and physical properties and thus must be determined by comparison to a reference standard, typically using a cell-based bioassay. This lack of an absolute method for determining potency, along with test method variability and potential for bias make assignment and monitoring of reference standard potency a major challenge during pharmaceutical development and manufacturing. The reference standard links the potency of dosages administered to the patient with those of original clinical studies. Therefore, the assignment of potency to biotherapeutic reference standards is vital for assuring the quality of medicines for patients. In this work, we propose a comprehensive roadmap for assigning potency to reference standards that is compliant with the two-tier system of standards as recommended in regulatory guidance. The roadmap includes statistical approaches for study design and acceptance criteria that are risk-based and phase-appropriate. It also provides mitigation approaches for potential assay bias.

Purity estimation of seized stimulant-type new psychoactive substances without reference standards by nitrogen chemiluminescence detection combined with GC-APCI-QTOFMS

Purity assessment of seized material containing new psychoactive substances (NPS) is complicated without appropriate primary reference standards. Here we present a method for fast quantitative estimation of stimulant-type NPS with use of secondary reference standards, based on gas chromatography nitrogen chemiluminescence detection coupled with atmospheric pressure chemical ionization quadrupole time-of-flight mass spectrometry (GC-NCD-APCI-QTOFMS). Quantification was based on the detector's N-equimolar response to nitrogen and using two external nitrogen-containing calibrators, MDMA for prim- and sec-amines and α-PVP for tert-amines. Sample preparation involved dissolving the seized powdery material in an organic solvent mixture followed by acylation with N-methyl-bis-trifluoroacetamide (MBTFA). The method's between-day accuracy and precision over a five-day period was measured for twenty-eight stimulants: the grand mean equimolarity was 91.9% (CV 5.5%), as compared with primary reference standards. The GC-NCD-APCI-QTOFMS method was applied to the purity estimation of forty-two seized powder samples previously found to contain stimulant-type NPS by appropriate methods. The quantitative results were compared to those obtained by an established method relying on liquid chromatography chemiluminescence detection (LC-CLND), the latter using caffeine as an external calibrator. The mean difference of purity values between the methods was 8.1% (range 0.4-26.7%). The presented method might find use as a tool for instant purity assessment in forensic laboratories.

Evaluating Diagnostic Tests for Helicobacter pylori Infection Without a Reference Standard: Use of Latent Class Analysis

Evaluation of diagnostic tests requires reference standards, which are often unavailable. Latent class analysis (LCA) can be used to evaluate diagnostic tests without reference standards, using a combination of observed and estimated results. Conditionally independent diagnostic tests for Helicobacter pylori infection are required. We used LCA to construct a reference standard and evaluate the capability of non-invasive tests (stool antigen test and serum antibody test) to diagnose H. pylori infection compared with the conventional method, where histology is the reference standard. A total of 96 healthy subjects with endoscopy histology results were enrolled from January to July 2016. Sensitivity and specificity were determined for the LCA approach (i.e., using a combination of three tests as the reference standard) and the conventional method. When LCA was used, sensitivity and specificity were 83.8% and 99.4% for histology, 80.0% and 81.9% for the stool antigen test, and 63.6% and 89.3% for the serum antibody test, respectively. When the conventional method was used, sensitivity and specificity were 75.8% and 71.1% for the stool antigen test and 77.7% and 60.7% for the serum antibody test, respectively. LCA can be applied to evaluate diagnostic tests that lack a reference standard.

Determining the Reliability of a New Method for Measuring Joint Range of Motion Through a Randomized Controlled Trial

Objective

To compare the reliability and validity of the Korean range of motion standard protocol (KRSP) for measuring joint range of motion (ROM) with those of the conventional ROM measurement using a goniometer.

Methods

We conducted a randomized controlled trial involving 91 healthy elderly individuals. We compared two strategies of measuring joint ROM to evaluate the reliability and validity of each standardized protocol: first, the KRSP based on the Chungnam National University guidelines and second, handheld goniometric measurement. In the first strategy, 3 examiners (1 rehabilitation doctor, 1 physical therapist, and 1 physical therapy student) independently measured joint ROM in 46 randomly selected subjects; in the second strategy, another 3 examiners (1 rehabilitation doctor, 1 physical therapist, and 1 physical therapy student) measured joint ROM in 45 randomly selected subjects. The reliability of each protocol was calculated using intraclass correlation coefficient, ICC(2,1), and root mean square error (RMSE).

Results

Both protocols showed good to excellent intra-rater reliability. With goniometer use, the inter-rater reliability was low—ICC(2,1), 95% confidence interval ranged from 0.643 (0.486–0.783) to -0.078 (-0.296–0.494)— and RMSE was high. With the KRSP, the inter-rater reliability ranged from 0.846 (0.686–0.931) to 0.986 (0.972–0.994) and RMSE was low.

Conclusion

ROM measurements using the KRSP showed excellent reliability. These results indicate that this protocol can be the reference standard for measuring ROM in clinical settings as an alternative to goniometers.

Single-calibrant quantification of seized synthetic opioids by liquid chromatography-chemiluminescence nitrogen detection

Drug seizures involving a wide variety of emerging new psychoactive substances (NPS) call for new approaches for instant quantification and valuation. Liquid chromatography-chemiluminescence nitrogen detection (LC-CLND) was used in the quantification of opioids with a single secondary standard (caffeine), utilizing the detector's equimolar response to nitrogen. The mean N-equimolarity of CLND for ten fentanyl derivatives and U-47700 by the present LC-CLND method was 96.4% (range 91-101%). The furanylfentanyl samples consisted of 112 powdery samples with a mean (median, range) hydrochloride purity of 13% (4.9%, 0.08-100%). The purity distribution of the furanylfentanyl samples was distinctly bipartite, showing only lower than 9% (N=98) and higher than 60% (N=14) purities. The carfentanil samples consisted of eight brownish sticky samples with a mean (median, range) hydrochloride purity of 0.064% (0.063%, 0.052-0.092%). The U-47700 samples consisted of seven powdery samples with a mean (median, range) hydrochloride purity of 89.0% (100%, 51-100%). The present application to synthetic opioid analysis widens the scope of the established LC-CLND method, previously found useful for single-calibrant quantification of stimulant/hallucinogenic and cannabinoid type of NPS.

Fuzzy gold standards: Approaches to handling an imperfect reference standard

There are many challenging aspects to the design, conduct and interpretation of a diagnostic test accuracy study. Given the utilisation of digital technology in dentistry the issues and complexities of how these new technologies can be compared to potentially 'fuzzy gold standards' needs to be addressed. This narrative aims to provide the reader with a brief review of the nature of such studies, and in particular to introduce the reader to issues in the choice and use of clinical reference standards. Potential solutions to problems of differential verification and the use of imperfect reference standards will be provided.

An analysis reveals differences between pragmatic and explanatory diagnostic accuracy studies

OBJECTIVES

The objective of this study was to clarify a difference between two approaches while evaluating the diagnostic accuracy of medical tests, labeled here as "pragmatic" vs. "explanatory" studies.

METHODS

Using the definitions and characteristics described by Schwartz and Lellouch for randomized trials of interventions, and Schwartz' more general distinction between a pragmatic and an explanatory approach in medical research, we define a similar continuum for diagnostic accuracy studies. Explanatory studies aim to better understand the behavior of a test; pragmatic ones are done to support recommendations or decisions about using the test in clinical practice.

RESULTS

Pragmatic test accuracy studies differ from explanatory test accuracy studies in several ways. The difference in aims has implications for key elements of study design, such as the study eligibility criteria, the recruitment of patients, the reference standard, and the choice of the statistical analysis. Explanatory accuracy studies are often designed to test a hypothesis. They are typically selective in recruitment, may include "healthy controls," with a small sample size, often recruited at a single center. They ignore testing failures in the analysis and more often present their results as ROC curves. By contrast, pragmatic studies are designed to guide decision making. They ideally will recruit a single, large, and representative group of patients at multiple sites and will more often present their results as estimates of sensitivity and specificity or predictive values at a prespecified threshold.

CONCLUSION

Distinguishing between a pragmatic and an explanatory approach can help in the design, analysis, and interpretation of diagnostic accuracy studies. It can clarify debates about the appropriateness of design features to the study purpose and about the validity and applicability of study findings.

Expert panel diagnosis demonstrated high reproducibility as reference standard in infectious diseases

OBJECTIVE

If a gold standard is lacking in a diagnostic test accuracy study, expert diagnosis is frequently used as reference standard. However, interobserver and intraobserver agreements are imperfect. The aim of this study was to quantify the reproducibility of a panel diagnosis for pediatric infectious diseases.

STUDY DESIGN AND SETTING

Pediatricians from six countries adjudicated a diagnosis (i.e., bacterial infection, viral infection, or indeterminate) for febrile children. Diagnosis was reached when the majority of panel members came to the same diagnosis, leaving others inconclusive. We evaluated intraobserver and intrapanel agreement with 6 weeks and 3 years' time intervals. We calculated the proportion of inconclusive diagnosis for a three-, five-, and seven-expert panel.

RESULTS

For both time intervals (i.e., 6 weeks and 3 years), intrapanel agreement was higher (kappa 0.88, 95%CI: 0.81-0.94 and 0.80, 95%CI: NA) compared to intraobserver agreement (kappa 0.77, 95%CI: 0.71-0.83 and 0.65, 95%CI: 0.52-0.78). After expanding the three-expert panel to five or seven experts, the proportion of inconclusive diagnoses (11%) remained the same.

CONCLUSION

A panel consisting of three experts provides more reproducible diagnoses than an individual expert in children with lower respiratory tract infection or fever without source. Increasing the size of a panel beyond three experts has no major advantage for diagnosis reproducibility.

Establishment of the First National Reference Standard for Insulin Lispro: Report of a collaborative study

The present study was aimed to establish the First National Reference Standard (NRS) for Insulin lispro to allow stakeholders including manufacturer's laboratories, drug testing laboratories, drug regulatory authorities and academic institutions to demonstrate accuracy of the test results and to enable comparison and validation of analytical methods. The candidate standard for Insulin lispro was evaluated in a collaborative study to assign the vial content in order to serve it as NRS to support the Indian Pharmacopoeia (IP) monograph. The candidate standard was calibrated against the Ph. Eur. Insulin lispro reference standard by each of six participant laboratories in India using HPLC assay method as per the requirements of IP monograph. The results indicate that the candidate standard has an average content of 5.79 mg per vial with purity of 99.87%. Based on the study results the candidate standard was judged suitable to serve as the first NRS for Insulin lispro.

The authors reply: Letter on: "Pitfalls in the measurement of muscle mass: a need for a reference standard" by Clark et al

However, semantics aside, we think that DXA can indeed serve as a reference standard for measuring muscle mass. Obviously, CT and MRI are advanced techniques that can and have been used to obtain important information such as muscle size/volume and more recently amount and distribution of intra- and intermuscular adipose tissue. Also individual muscles can be assessed separately. However, with respect to muscle mass, the comparison of DXA with CT/MRI is rather difficult because DXA and QCT/MRI measure different physical parameters.

Pitfalls in the measurement of muscle mass: a need for a reference standard

BACKGROUND

All proposed definitions of sarcopenia include the measurement of muscle mass, but the techniques and threshold values used vary. Indeed, the literature does not establish consensus on the best technique for measuring lean body mass. Thus, the objective measurement of sarcopenia is hampered by limitations intrinsic to assessment tools. The aim of this study was to review the methods to assess muscle mass and to reach consensus on the development of a reference standard.

METHODS

Literature reviews were performed by members of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis working group on frailty and sarcopenia. Face-to-face meetings were organized for the whole group to make amendments and discuss further recommendations.

RESULTS

A wide range of techniques can be used to assess muscle mass. Cost, availability, and ease of use can determine whether the techniques are better suited to clinical practice or are more useful for research. No one technique subserves all requirements but dual energy X-ray absorptiometry could be considered as a reference standard (but not a gold standard) for measuring muscle lean body mass.

CONCLUSIONS

Based on the feasibility, accuracy, safety, and low cost, dual energy X-ray absorptiometry can be considered as the reference standard for measuring muscle mass.

Designing image segmentation studies: Statistical power, sample size and reference standard quality

Segmentation algorithms are typically evaluated by comparison to an accepted reference standard. The cost of generating accurate reference standards for medical image segmentation can be substantial. Since the study cost and the likelihood of detecting a clinically meaningful difference in accuracy both depend on the size and on the quality of the study reference standard, balancing these trade-offs supports the efficient use of research resources. In this work, we derive a statistical power calculation that enables researchers to estimate the appropriate sample size to detect clinically meaningful differences in segmentation accuracy (i.e. the proportion of voxels matching the reference standard) between two algorithms. Furthermore, we derive a formula to relate reference standard errors to their effect on the sample sizes of studies using lower-quality (but potentially more affordable and practically available) reference standards. The accuracy of the derived sample size formula was estimated through Monte Carlo simulation, demonstrating, with 95% confidence, a predicted statistical power within 4% of simulated values across a range of model parameters. This corresponds to sample size errors of less than 4 subjects and errors in the detectable accuracy difference less than 0.6%. The applicability of the formula to real-world data was assessed using bootstrap resampling simulations for pairs of algorithms from the PROMISE12 prostate MR segmentation challenge data set. The model predicted the simulated power for the majority of algorithm pairs within 4% for simulated experiments using a high-quality reference standard and within 6% for simulated experiments using a low-quality reference standard. A case study, also based on the PROMISE12 data, illustrates using the formulae to evaluate whether to use a lower-quality reference standard in a prostate segmentation study.

Interlaboratory study for the establishment of Brazilian Bothrops Reference Venom and Antivenom for potency evaluation of Bothrops antivenom

A collaborative study was performed for the establishment of the 5th lot of Brazilian Bothrops Reference Venom and the 1st lot of Brazilian Bothrops Reference Antivenom. All Brazilian manufacturers of Antibothrops Immunoglobulins and the National Control Laboratory participated of the study. The declared potency of the 5th lot of the Bothrops Reference Venom is 40.29 μg/0.5 ml, and the potency of the 1st lot of Bothrops Reference Antivenom is 6.51 mg/ml. For the potency evaluation of Bothrops Reference Venom the inter assay precision (gCV) was 3.25% in lab 01; 3.51% in INCQS; 4.71% in lab 03 and 25.11% in lab 02, and the inter laboratory precision was 13.76%. The intra assay precision of Bothrops Reference Antivenom determinations was 4.38% in INCQS; 8.47% in lab 02; 10.51% in lab 03 and 20.05% in lab 01. The inter assay precision was 3.51% in INCQS; 9.65% in lab 02; 18.03% in lab 01 and 20.23% in lab 03. The inter laboratory precision was 15.85%. Despite the high number of invalid results (55.6% for the pharmacopoeial method and 69.4% for the proposed method) the parallel line assay, have better inter laboratorial precision (gCV = 16.62%) than the pharmacopoeial potency assay (gCV = 38.28%).

The danish regions pediatric triage model has a limited ability to detect both critically ill children as well as children to be sent home without treatment - a study of diagnostic accuracy

Background

The Danish Regions Pediatric Triage model (DRPT) was introduced in 2012 and subsequent implemented in most Danish acute pediatric departments. The aim was to evaluate the validity of DRPT as a screening tool to detect both the most serious acute conditions and the non-serious conditions in the acute referred patients in a pediatric department.

Method

The study was prospective observational, with follow-up on all children with acute referral to pediatric department from October to December 2015. The DRPT was evaluated by comparison to a predefined reference standard and to the actual clinical outcomes: critically ill children and children returned to home without any treatment. The sensitivity, specificity, positive predictive value, negative predictive value, accuracy and likelihood for positive and negative test were calculated.

Results

Five hundred fifty children were included. The DRPT categorized 7% very urgent, 28% urgent, 29% standard and 36% non-urgent. The DRPT was equal to the reference standard in 31% of the children (CI: 27-35%). DRPT undertriaged 55% of the children (CI: 51-59%) and overtriaged 14% of the children (CI: 11-17%). For the most urgent patients the sensitivity of DRPT was 31% (CI: 20-48%) compared to the reference standard and 20% (CI: 7-41) for critically ill. For children with non-urgent conditions the specificity of DRPT was 66% (CI: 62-71%) compared to the reference standard and 68% (CI: 62-75%) for the children who went home with no treatment. In none of the analyses, the likelihood ratio of the negative test was less than 0.7 and the positive likelihood ratio only reached more than 5 in one of the analyses.

Discussion

This study is the first to evaluate the DRPT triage system. From the very limited validity studies of other well-established triage systems, it is difficult to judge whether the DRPT performs better or worse than the alternatives. The DRPT errs to the undertriage side. If the sensitivity is low, a number of the sickest children are undetected and this is a matter of concern.

Conclusion

The DRPT is a triage tool with limited ability to detect the critically ill children as well as the children who can be returned to home without any treatment.

Trial registration

Not relevant

Electronic supplementary material

The online version of this article (doi:10.1186/s13049-017-0397-6) contains supplementary material, which is available to authorized users.

Establishment of the 2nd Korean national biological reference standard for blood coagulation factor VIII:C concentrate

Since the 1st Korean national biological reference standard for factor (F)VIII concentrate, established in 2001, has shown declining potency, we conducted this study to replace this standard with a 2nd Korean national biological reference standard for blood coagulation FVIII concentrate. The candidate materials for the 2nd standard were prepared in 8000 vials with 10 IU/ml of target potency, according to the approved manufacturing process of blood coagulation Factor VIII:C Monoclonal Antibody-purified, Freeze-dried Human Blood Coagulation Factor VIII:C. Potency was evaluated by one-stage clotting and chromogenic methods and the stability was confirmed to meet the specifications during a period of 73 months. Since the potencies obtained by the two methods differed significantly (P < 0.015), the values were determined separately according to the geometric means (8.9 and 7.4 IU/vial, respectively). The geometric coefficients of interlaboratory variability were 3.4% and 7.6% by the one-stage clotting and chromogenic assays, respectively.

The adverse impact of surveillance intervals on the sensitivity of FDG-PET/CT for the detection of distant metastases in head and neck cancer patients

The presence of distant metastases at initial evaluation influences treatment selection, since no effective systemic treatment for disseminated head and neck squamous cell carcinoma (HNSCC) is currently available. The reported sensitivity for the detection of distant metastases by contrast-enhanced (ce)CT and FDG-PET(/CT) differs substantially between studies. We hypothesized that these sensitivity values are highly dependent on the reference standard use, e.g., follow-up term. Therefore, we analyze our results of FDG-PET/CT (including chest ceCT) with long-term follow-up and compare these findings with data from the literature, with particular interest in the different reference standards. Forty-six HNSCC patients with high-risk factors underwent pretreatment screening for distant metastases by FDG-PET/CT (including chest ceCT). In 16 (35%) patients, distant metastases were detected during screening (6 patients) or during a mean follow-up of 39.4 months after screening (10 patients). The sensitivity and negative predictive value were 83.3 and 97.2% when 6 months, 60.0 and 89.9% when 12 months, and 37.5 and 72.2% when 30 months follow-up were used as reference standard, respectively. This is comparable with reported studies with similar reference standards. This critical appraisal on the reference standards used in our and reported studies shows room for improvement for the detection of distant metastases to refrain more patients from unnecessary extensive locoregional treatment for occult metastatic HNSCC.

Culture is an imperfect and heterogeneous reference standard in pediatric tuberculosis

BACKGROUND

In pediatric tuberculosis (pTB), culture is the accepted reference standard for assessing new diagnostic tests despite culture only confirming 10-50% of clinically diagnosed cases.

METHODS

Using the studies previously included in the systematic review of Gene Xpert, we evaluated the diagnostic yield of culture. Children with symptoms and signs suggestive of TB were considered to have a clinical diagnosis if they were 1) culture positive or 2) followed clinically for at least one month and started on Anti-Tuberculosis Therapy (ATT).

RESULTS

Of 1989 children with presumptive pTB, 229 (11.5%) had culture-confirmation. Of the remaining 1760 culture negative children, 710 (24.4) were classified as culture-negative clinical TB and 821 were classified as "not TB". Diagnostic yield of culture was 24.4% (median 28.7% IQR 15.6%-42.4%; range 1.5%-65%).

CONCLUSION

Culture, the accepted reference standard for pediatric TB diagnostics, has a low and variable yield that impacts how diagnostic studies should be reported as well as everyday clinical care.

Establishment of an equine tetanus antitoxin reference standard for veterinary use in Japan

To establish the first National Veterinary Assay Laboratory (NVAL) equine tetanus antitoxin reference standard for veterinary use, we manufactured vials of a candidate antitoxin. These were quality tested for moisture content, vacuum, colour, clarity, and the presence of foreign objects. Ultimately, 115 quality-controlled vials were prepared. To estimate the antitoxin potency of the candidate standard, three different laboratories conducted parallel line assays alongside the existing antitoxin standard. These potency estimates ranged from 38 to 42 IU. This activity was maintained for two years after manufacture, as compared with a fresh vial. No statistically significant non-linearity or non-parallelism of the regression lines was observed (p > 0.05). Statistical assessment of inter- and intra-laboratory variability revealed acceptable coefficients of variation of 3.2% and 2.4-3.1%, respectively. Based on these results, the potency of the potential reference standard was calculated at 40 units of antitoxin activity per 1-mL vial. Vials of this preparation were distributed for use as the first equine tetanus antitoxin reference standard for veterinary use in September 2015.

Different reference BMDs affect the prevalence of osteoporosis

The T score represents the degree of deviation from the peak bone mineral density (BMD) (reference standard) in a population. Little has been investigated concerning the age at which the BMD reaches the peak value and how we should define the reference standard BMD in terms of age ranges. BMDs of 9,800 participants were analyzed from the Korean National Health and Nutrition Examination Survey database. Five reference standards were defined: (1) the reference standard of Japanese young adults provided by the dual-energy X-ray absorptiometry machine manufacturer, (2) peak BMD of the Korean population evaluated by statistical analysis (second-order polynomial regression models), (3) BMD of subjects aged 20-29 years, (4) BMD of subjects aged 20-39 years, and (5) BMD of subjects aged 30-39 years. T-scores from the five reference standards were calculated, and the prevalence of osteoporosis was evaluated and compared for males and females separately. The peak BMD in the polynomial regression model was achieved at 26 years in males and 36 years in females in the total hip, at 20 years in males and 27 years in females in the femoral neck, and at 20 years in males and 30 years in females in the lumbar spine. The prevalence of osteoporosis over the age of 50 years showed significant variation of up to two fold depending on the reference standards adopted. The age at which peak BMD was achieved was variable according to the gender and body sites. A consistent definition of peak BMD needs to be established in terms of age ranges because this could affect the prevalence of osteoporosis and healthcare policies.

DXA: Technical aspects and application

The key role of dual-energy X-ray absorptiometry (DXA) in the management of metabolic bone diseases is well known. The role of DXA in the study of body composition and in the clinical evaluation of disorders which directly or indirectly involve the whole metabolism as they may induce changes in body mass and fat percentage is less known or less understood. DXA has a range of clinical applications in this field, from assessing associations between adipose or lean mass and the risk of disease to understanding and measuring the effects of pathophysiological processes or therapeutic interventions, in both adult and paediatric human populations as well as in pre-clinical settings. DXA analyses body composition at the molecular level that is basically translated into a clinical model made up of fat mass, non-bone lean mass, and bone mineral content. DXA allows total and regional assessment of the three above-mentioned compartments, usually by a whole-body scan. Since body composition is a hot topic today, manufacturers have steered the development of DXA technology and methodology towards this. New DXA machines have been designed to accommodate heavier and larger patients and to scan wider areas. New strategies, such as half-body assessment, permit accurate body scan and analysis of individuals exceeding scan field limits. Although DXA is a projective imaging technique, new solutions have recently allowed the differential estimate of subcutaneous and intra-abdominal visceral fat. The transition to narrow fan-beam densitometers has led to faster scan times and better resolution; however, inter- or intra-device variation exists depending on several factors. The purposes of this review are: (1) to appreciate the role of DXA in the study of body composition; (2) to understand potential limitations and pitfalls of DXA in the analysis of body composition; (3) to learn about technical elements and methods, and to become familiar with biomarkers in DXA.

6-week radiographs unsuitable for diagnosis of suspected scaphoid fractures

INTRODUCTION

Six week follow-up radiographs are a common reference standard for the diagnosis of suspected scaphoid fractures. The main purpose of this study was to evaluate the interobserver reliability and diagnostic performance characteristics of 6-weeks radiographs for the detection of scaphoid fractures. In addition, two online techniques for evaluating radiographs were compared.

MATERIALS AND METHODS

A total of 81 orthopedic surgeons affiliated with the Science of Variation Group assessed initial and 6-week scaphoid-specific radiographs of a consecutive series of 34 patients with suspected scaphoid fractures. They were randomized in two groups for evaluation, one used a standard website showing JPEG files and one a more sophisticated image viewer (DICOM). The goal was to identify the presence or absence of a (consolidated) scaphoid fracture. Interobserver reliability was calculated using the multirater kappa measure. Diagnostic performance characteristics were calculated according to standard formulas with CT and MRI upon presentation in the emergency department as reference standards.

RESULTS

The interobserver agreement of 6-week radiographs for the diagnosis of scaphoid fractures was slight for both JPEG and DICOM (k = 0.15 and k = 0.14, respectively). The sensitivity (range 42-79 %) and negative predictive value (range 79-94 %) were significantly higher using a DICOM viewer compared to JPEG images. There were no differences in specificity (range 53-59 %), accuracy (range 53-58 %), and positive predictive value (range 14-26 %) between the groups.

CONCLUSIONS

Due to low agreement between observers for the recognition of scaphoid fractures and poor diagnostic performance, 6-week radiographs are not adequate for evaluating suspected scaphoid fractures. The online evaluation of radiographs using a DICOM viewer seem to improve diagnostic performance characteristics compared to static JPEG images and future reliability and diagnostic studies should account for variation due to the method of delivering medical images.

LEVEL OF EVIDENCE

Diagnostic level II.

Baseline MDCT findings after prosthetic heart valve implantation provide important complementary information to echocardiography for follow-up purposes

OBJECTIVES

Recent studies have proposed additional multidetector-row CT (MDCT) for prosthetic heart valve (PHV) dysfunction. References to discriminate physiological from pathological conditions early after implantation are lacking. We present baseline MDCT findings of PHVs 6 weeks post implantation.

METHODS

Patients were prospectively enrolled and TTE was performed according to clinical guidelines. 256-MDCT images were systematically assessed for leaflet excursions, image quality, valve-related artefacts, and pathological and additional findings.

RESULTS

Forty-six patients were included comprising 33 mechanical and 16 biological PHVs. Overall, MDCT image quality was good and relevant regions remained reliably assessable despite mild-moderate PHV-artefacts. MDCT detected three unexpected valve-related pathology cases: (1) prominent subprosthetic tissue, (2) pseudoaneurysm and (3) extensive pseudoaneurysms and valve dehiscence. The latter patient required valve surgery to be redone. TTE only showed trace periprosthetic regurgitation, and no abnormalities in the other cases. Additional findings were: tilted aortic PHV position (n = 3), pericardial haematoma (n = 3) and pericardial effusion (n = 3). Periaortic induration was present in 33/40 (83 %) aortic valve patients.

CONCLUSIONS

MDCT allowed evaluation of relevant PHV regions in all valves, revealed baseline postsurgical findings and, despite normal TTE findings, detected three cases of unexpected, clinically relevant pathology.

KEY POINTS

• Postoperative MDCT presents baseline morphology relevant for prosthetic valve follow-up. • 83 % of patients show periaortic induration 6 weeks after aortic valve replacement. • MDCT detected three cases of clinically relevant pathology not found with TTE. • Valve dehiscence detection by MDCT required redo valve surgery in one patient. • MDCT is a suitable and complementary imaging tool for follow-up purposes.

Selection of reference standard during method development using the analytical hierarchy process

Reference standard is critical for ensuring reliable and accurate method performance. One important issue is how to select the ideal one from the alternatives. Unlike the optimization of parameters, the criteria of the reference standard are always immeasurable. The aim of this paper is to recommend a quantitative approach for the selection of reference standard during method development based on the analytical hierarchy process (AHP) as a decision-making tool. Six alternative single reference standards were assessed in quantitative analysis of six phenolic acids from Salvia Miltiorrhiza and its preparations by using ultra-performance liquid chromatography. The AHP model simultaneously considered six criteria related to reference standard characteristics and method performance, containing feasibility to obtain, abundance in samples, chemical stability, accuracy, precision and robustness. The priority of each alternative was calculated using standard AHP analysis method. The results showed that protocatechuic aldehyde is the ideal reference standard, and rosmarinic acid is about 79.8% ability as the second choice. The determination results successfully verified the evaluation ability of this model. The AHP allowed us comprehensive considering the benefits and risks of the alternatives. It was an effective and practical tool for optimization of reference standards during method development.

Abdominal adiposity by ultrasonography: a "pocket" database for reference standard in Italian people

AIMS

To provide a reference standard database of ultrasonographic parameters of abdominal adiposity in healthy people.

METHODS

Italian non-obese volunteers among blood donors were enrolled in 5 age bands (from 18 to 70 year-old) to reach the threshold of 25 males and 25 females per single band (total: 250). All subjects were measured for weight, height and waist circumference and underwent ultrasonography (US) by an expert radiologist for the assessment of several abdominal fat thicknesses (minimum and maximum subcutaneous fat thickness, maximum preperitoneal fat thickness, intrabdominal fat thickness, aorto-mesenteric thickness, and mesenteric fat thickness). In addition, US data were normalized per waist circumference.

RESULTS

From 30s to 50s no statistically significant differences were achieved between males and females for the adiposity markers of visceral fat, while a relevant divergence was proved from 60s to 70s. During ageing a marked increase of the visceral fat compartment was observed in males, while only the preperitoneal circumference was significantly modified in females.

CONCLUSIONS

This paper reports on US parameters of abdominal adiposity of healthy Italian adults, to be used as a reference for daily clinical practice. Data could be also considered as control group for future investigations on physiology, pathological conditions, and differences between countries.

Testing for interchangeability of imaging tests

RATIONALE AND OBJECTIVES

New tests are typically assessed by estimating their technical and diagnostic performance through comparisons with a reference standard. A valid reference standard, however, is not always available and is not required for assessing the interchangeability of a new test with an existing one.

MATERIALS AND METHODS

To show interchangeability of a new test with an existing test, one compares the differences in diagnoses between the new and existing tests to differences between diagnoses made with the existing test on several occasions. We illustrate the test for interchangeability with two studies. In a transcatheter aortic valve replacement study, we test whether semiautomated analysis can be used interchangeably with manual reconstructions from three-dimensional computed tomography (CT) images. In patients with femoroacetabular impingement, we test whether magnetic resonance imaging (MRI) can replace CT to measure acetabular version.

RESULTS

Although the semiautomated method agreed often with the manual measurement of aortic valve size (87.6%), interchanging the semiautomated method with manual measurements by an expert would lead to a 1.7%-12.2% increase in the frequency of disagreement. Interchanging MRI for CT to measure acetabular version would lead to differences in angle measurements of 2.0° to 3.1° in excess of the differences we would expect to see with CT alone.

CONCLUSIONS

Testing for agreement or correlation between a new and an existing test is not sufficient evidence of the performance of a new test. A formal evaluation of interchangeability can be conducted in the absence of a reference standard.

Application of quantitative 1H NMR for the calibration of protoberberine alkaloid reference standards

Quantitative nuclear magnetic resonance spectroscopy (qNMR) has been developed into an important tool in the drug analysis, biomacromolecule detection, and metabolism study. Compared with mass balance method, qNMR method bears some advantages in the calibration of reference standard (RS): it determines the absolute amount of a sample; other chemical compound and its certified reference material (CRM) can be used as internal standard (IS) to obtain the purity of the sample. Protoberberine alkaloids have many biological activities and have been used as reference standards for the control of many herbal drugs. In present study, the qNMR methods were developed for the calibration of berberine hydrochloride, palmatine hydrochloride, tetrahydropalmatine, and phellodendrine hydrochloride with potassium hydrogen phthalate as IS. Method validation was carried out according to the guidelines for the method validation of Chinese Pharmacopoeia. The results of qNMR were compared with those of mass balance method and the differences between the results of two methods were acceptable based on the analysis of estimated measurement uncertainties. Therefore, qNMR is an effective and reliable analysis method for the calibration of RS and can be used as a good complementarity to the mass balance method.