Adjusting for Differential-verification Bias in Diagnostic-accuracy Studies

Screening for Primary Aldosteronism by Mass Spectrometry Versus Immunoassay Measurements of Aldosterone: A Prospective Within-Patient Study

BACKGROUND

Measurements of aldosterone by mass spectrometry are more accurate and less prone to interferences than immunoassay measurements, and may produce a more accurate aldosterone:renin ratio (ARR) when screening for primary aldosteronism (PA).

METHODS

Differences in diagnostic performance of the ARR using mass spectrometry vs immunoassay measurements of aldosterone were examined in 710 patients screened for PA. PA was confirmed in 153 patients and excluded in 451 others. Disease classifications were not achieved in 106 patients. Areas under receiver-operating characteristic curves (AUROC) and other measures were used to compare diagnostic performance.

RESULTS

Mass spectrometry-based measurements yielded lower plasma aldosterone concentrations than immunoassay measurements. For the ARR based on immunoassay measurements of aldosterone, AUROCs were slightly lower (P = 0.018) than those using mass spectrometry measurements (0.895 vs 0.906). The cutoff for the ARR to reach a sensitivity of 95% was 30 and 21.5 pmol/mU by respective immunoassay and mass spectrometry-based measurements, which corresponded to specificities of 57% for both. With data restricted to patients with unilateral PA, diagnostic sensitivities of 94% with specificities >81% could be achieved at cutoffs of 68 and 52 pmol/mU for respective immunoassay and mass spectrometry measurements.

CONCLUSIONS

Mass spectrometry-based measurements of aldosterone for the ARR provide no clear diagnostic advantage over immunoassay-based measurements. Both approaches offer limited diagnostic accuracy for the ARR as a screening test. One solution is to employ the higher cutoffs to triage patients likely to have unilateral PA for further tests and possible adrenalectomy, while using the lower cutoffs to identify others for targeted medical therapy.German Clinical Trials Register ID: DRKS00017084.

Statistical methods for evaluating the fine needle aspiration cytology procedure in breast cancer diagnosis

Background

Statistical issues present while evaluating a diagnostic procedure for breast cancer are non rare but often ignored, leading to biased results. We aimed to evaluate the diagnostic accuracy of the fine needle aspiration cytology(FNAC), a minimally invasive and rapid technique potentially used as a rule-in or rule-out test, handling its statistical issues: suspect test results and verification bias.

Methods

We applied different statistical methods to handle suspect results by defining conditional estimates. When considering a partial verification bias, Begg and Greenes method and multivariate imputation by chained equations were applied, however, and a Bayesian approach with respect to each gold standard was used when considering a differential verification bias. At last, we extended the Begg and Greenes method to be applied conditionally on the suspect results.

Results

The specificity of the FNAC test above 94%, was always higher than its sensitivity regardless of the proposed method. All positive likelihood ratios were higher than 10, with variations among methods. The positive and negative yields were high, defining precise discriminating properties of the test.

Conclusion

The FNAC test is more likely to be used as a rule-in test for diagnosing breast cancer. Our results contributed in advancing our knowledge regarding the performance of FNAC test and the methods to be applied for its evaluation.

Supplementary Information

The online version contains supplementary material available at (10.1186/s12874-022-01506-y).

Reliability of Interleukin-6 Alone and in Combination for Diagnosis of Early Onset Neonatal Sepsis: Systematic Review

Neonatal sepsis is a major cause of morbidity and mortality in both preterm and term infants. Early-onset neonatal sepsis (EONS) presents within the first 72 h of life. Diagnosis is difficult as signs and symptoms are non-specific, and inflammatory markers are widely used to confirm or rule out neonatal sepsis. Interleukin-6 (IL-6) is part of the fetal inflammatory response syndrome (FIRS) and therefore an interesting early marker for neonatal sepsis. The main objective for this review was to assess the diagnostic potential of IL-6, alone and in combination, for diagnosis of early neonatal sepsis (EONS) in term and preterm infants, in cord and peripheral blood, and in dependence of timing of sample collection. IL-6 diagnostic accuracy studies for diagnosing EONS published between 1990 and 2020 were retrieved using the PubMed database. We included 31 out of 204 articles evaluating the potential of IL-6 for the diagnosis of EONS in a study population of newborns with culture-proven and/or clinically suspected sepsis. We excluded articles dealing with neonatal bacterial infections other than sepsis and biomarkers other than inflammatory markers, those written in languages other than English or German, studies that did not distinguish between EONS and late-onset sepsis, and animal and in vitro studies. Full-text articles were checked for other relevant studies according to the PRISMA criteria. We identified 31 studies on IL-6 diagnostic accuracy for EONS diagnosis between 1990 and 2020 including a total of 3,276 infants. Sensitivity and specificity were reported, and subgroup analysis was performed. A STARD checklist adapted for neonates with neonatal sepsis was used for quality assessment. The range of IL-6 sensitivity and specificity in neonatal samples was 42.1-100% and 43-100%; the median values were 83 and 83.3%, respectively. IL-6 accuracy was better in preterm infants than in mixed-study populations. Early sample collection at the time of sepsis suspicion had the highest sensitivity when compared to other time points. Cord blood IL-6 had higher diagnostic value compared to peripheral blood. The biomarker combination of IL-6 and CRP was found to be highly sensitive, but poorly specific. Limitations of this review include use of only one database and inclusion of a heterogeneous group of studies and a small number of studies looking at biomarker combinations; a strength of this review is its focus on early-onset sepsis, since type of sepsis was identified as a significant source of heterogeneity in IL-6 diagnostic accuracy studies. We concluded that IL-6 has a good performance as an early diagnostic marker of EONS within a study population of preterm infants, with best results for cord blood IL-6 using cutoff values above 30 pg/ml.

Diagnostic accuracy of faecal calprotectin in a symptom-based algorithm for early diagnosis of inflammatory bowel disease adjusting for differential verification bias using a Bayesian approach

BACKGROUND

Diagnostic delay in IBD is a major problem and diagnosis is frequently arrived when irreversible damage has already occurred. This study evaluated accuracy of faecal calprotectin (fCAL) integrated with diagnostic criteria for early diagnosis of IBD in a primary care setting.

METHODS

General practitioners (GPs) were trained to recognize alarm symptoms for IBD classified as major and minor criteria. Fulfilment of one major or at least two minor criteria was followed by free fCAL testing and a visit by an IBD specialist and follow-up over 12 months. All patients with positive fCAL testing, i.e., ≥70 μg/g underwent colonoscopy. The diagnostic accuracy of fCAL was estimated after adjusting for differential-verification bias following a Bayesian approach.

RESULTS

Thirty-four GPs participated in the study and 133 patients were tested for fCAL between July 2016 and August 2017. Positivity of fCAL was seen in 45/133 patients (34%) and a final IBD diagnosis was made in 10/45 (22%). According to the threshold of 70 μg/g, fCAL achieved a sensitivity of 74.8% (95%CI: 39.10-96.01%), a specificity of 70.4% (95%CI: 61.76-78.16%) and an overall diagnostic accuracy of 70.6% (95%CI: 61.04-78.37%). As for prognostic accuracy, despite positive predictive value being low, 21.9% (95%CI: 11.74-35.18%), the negative predictive value was definitely higher: 96.2% (95%CI: 84.96-99.51%).

CONCLUSIONS

fCAL with a threshold set at 70 μg/g seems to represent a potentially reliable negative test to be used in primary care settings for patients with symptoms suggestive of IBD.

Comparison of MRI and VQ-SPECT as a Screening Test for Patients With Suspected CTEPH: CHANGE-MRI Study Design and Rationale

The diagnostic strategy for chronic thromboembolic pulmonary hypertension (CTEPH) is composed of two components required for a diagnosis of CTEPH: the presence of chronic pulmonary embolism and an elevated pulmonary artery pressure. The current guidelines require that ventilation-perfusion single-photon emission computed tomography (VQ-SPECT) is used for the first step diagnosis of chronic pulmonary embolism. However, VQ-SPECT exposes patients to ionizing radiation in a radiation sensitive population. The prospective, multicenter, comparative phase III diagnostic trial CTEPH diagnosis Europe - MRI (CHANGE-MRI, ClinicalTrials.gov identifier NCT02791282) aims to demonstrate whether functional lung MRI can serve as an equal rights alternative to VQ-SPECT in a diagnostic strategy for patients with suspected CTEPH. Positive findings are verified with catheter pulmonary angiography or computed tomography pulmonary angiography (gold standard). For comparing the imaging methods, a co-primary endpoint is used. (i) the proportion of patients with positive MRI in the group of patients who have a positive SPECT and gold standard diagnosis for chronic pulmonary embolism and (ii) the proportion of patients with positive MRI in the group of patients with negative SPECT and gold standard. The CHANGE-MRI trial will also investigate the performance of functional lung MRI without i.v. contrast agent as an index test and identify cardiac, hemodynamic, and pulmonary MRI-derived parameters to estimate pulmonary artery pressures and predict 6-12 month survival. Ultimately, this study will provide the necessary evidence for the discussion about changes in the recommendations on the diagnostic approach to CTEPH.

Global identifiability of latent class models with applications to diagnostic test accuracy studies: A Gröbner basis approach

Identifiability of statistical models is a fundamental regularity condition that is required for valid statistical inference. Investigation of model identifiability is mathematically challenging for complex models such as latent class models. Jones et al. used Goodman's technique to investigate the identifiability of latent class models with applications to diagnostic tests in the absence of a gold standard test. The tool they used was based on examining the singularity of the Jacobian or the Fisher information matrix, in order to obtain insights into local identifiability (ie, there exists a neighborhood of a parameter such that no other parameter in the neighborhood leads to the same probability distribution as the parameter). In this paper, we investigate a stronger condition: global identifiability (ie, no two parameters in the parameter space give rise to the same probability distribution), by introducing a powerful mathematical tool from computational algebra: the Gröbner basis. With several existing well-known examples, we argue that the Gröbner basis method is easy to implement and powerful to study global identifiability of latent class models, and is an attractive alternative to the information matrix analysis by Rothenberg and the Jacobian analysis by Goodman and Jones et al.

Case detection in primary aldosteronism: high-diagnostic value of the aldosterone-to-renin ratio when performed under standardized conditions

OBJECTIVE

The aldosterone-to-renin ratio is widely used and is the recommended screening modality for primary aldosteronism by the Endocrine Society Guideline. However, studies on its diagnostic accuracy have been inconsistent, which is mainly because of methodological limitations. We set out to evaluate this diagnostic value by using a highly standardized study protocol, which is in line with the Endocrine Society Guideline recommendations regarding indications for screening, testing conditions and reference standards in daily clinical practice.

METHODS

In this prospective study, 233 consecutive patients referred to the University Medical Center Utrecht with difficult-to-control hypertension were enrolled. In addition to aldosterone-to-renin ratio measurements, all patients underwent a saline infusion test as a reference standard. A plasma aldosterone concentration greater than 280 pmol/l after saline infusion was considered diagnostic for aldosteronism and the plasma renin activity was assessed to exclude patients with secondary aldosteronism from the final primary aldosteronism diagnosis.

RESULTS

Correlation of the aldosterone-to-renin ratio (cut-off >5) with primary aldosteronism diagnosis showed 16 true positive, 29 false positive, 188 true negative and 0 false negative aldosterone-to-renin ratios, resulting in a sensitivity of 100% (CI 75.9-100), specificity of 86.7% (CI 81.2-90.7), positive-predictive value of 35.6% (CI 22.3-51.3) and negative-predictive value of 100% (CI 97.5-100.0). The corresponding area under the curve was 0.933 (CI 0.900-0.966).

CONCLUSION

These findings show that the aldosterone-to-renin ratio is a good screening modality for primary aldosteronism and is without a high risk of missing a primary aldosteronism diagnosis whenever performed under well standardized conditions.

Accuracy of Computed Tomography in Diagnosis of Intra-abdominal Injuries in Stable Patients With Anterior Abdominal Stab Wounds: A Systematic Review and Meta-analysis

BACKGROUND

Workup for patients presenting to the emergency department (ED) following an anterior abdominal stab wound (AASW) has been debated since the 1960s. Experts agree that patients with peritonitis, evisceration, or hemodynamic instability should undergo immediate laparotomy (LAP); however, workup of stable, asymptomatic or nonperitoneal patients is not clearly defined.

OBJECTIVES

The objective was to evaluate the accuracy of computed tomography of abdomen and pelvis (CTAP) for diagnosis of intraabdominal injuries requiring therapeutic laparotomy (THER-LAP) in ED patients with AASW. Is a negative CT scan without a period of observation sufficient to safely discharge a hemodynamically stable, asymptomatic AASW patient?

METHODS

We searched PubMed, Embase, and Scopus from their inception until May 2017 for studies on ED patients with AASW. We defined the reference standard test as LAP for patients who were managed surgically and inpatient observation in those who were managed nonoperatively. In those who underwent LAP, THER-LAP was considered as disease positive. We used the Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS-2) to evaluate the risk of bias and assess the applicability of the included studies. We attempted to compute the pooled sensitivity, specificity, positive likelihood ratio (LR+), and negative likelihood ratio (LR-) using a random-effects model with MetaDiSc software and calculate testing and treatment thresholds for CT scan applying the Pauker and Kassirer model.

RESULTS

Seven studies were included encompassing 575 patients. The weighted prevalence of THER-LAP was 34.3% (95% confidence interval [CI] = 30.5%-38.2%). Studies had variable quality and the inclusion criteria were not uniform. The operating characteristics of CT scan were as follows: sensitivity = 50% to 100%, specificity = 39% to 97%, LR+ = 1.0 to 15.7, and LR- = 0.07 to 1.0. The high heterogeneity (I²  > 75%) of the operating characteristics of CT scan prevented pooling of the data and therefore the testing and treatment thresholds could not be estimated.

DISCUSSION

The articles revealed a high prevalence (8.7%, 95% CI = 6.1%-12.2%) of injuries requiring THER-LAP in patients with a negative CT scan and almost half (47%, 95% CI = 30%-64%) of those injuries involved the small bowel.

CONCLUSIONS

In stable AASW patients, a negative CT scan alone without an observation period is inadequate to exclude significant intraabdominal injuries.

Predicting inflammatory bowel disease in children with abdominal pain and diarrhoea: calgranulin-C versus calprotectin stool tests

OBJECTIVE

Calgranulin-C (S100A12) is a new faecal marker of inflammation that is potentially more specific for inflammatory bowel disease (IBD) than calprotectin, since it is only released by activated granulocytes. We compared calgranulin-C and calprotectin to see which of the two tests best predicted IBD in children with chronic abdominal pain and diarrhoea.

DESIGN

Delayed-type cross-sectional diagnostic study.

SETTING AND PATIENTS

Previously undiagnosed patients aged 6-17 years, who were seen in paediatric clinics in the Netherlands and Belgium, sent in a stool sample for analysis. Patients with a high likelihood of IBD underwent upper and lower endoscopy (ie, preferred reference test), while those with a low likelihood were followed for 6 months for latent IBD to become visible (ie, alternative reference test). We used Bayesian modelling to correct for differential verification bias.

MAIN OUTCOME MEASURES

Primary outcome was the specificity for IBD using predefined test thresholds (calgranulin-C: 0.75 µg/g, calprotectin: 50 µg/g). Secondary outcome was the test accuracy with thresholds based on receiver operating characteristics (ROC) analysis.

RESULTS

IBD was diagnosed in 93 of 337 patients. Calgranulin-C had significantly better specificity than calprotectin when predefined thresholds were used (97% (95% credible interval (CI) 94% to 99%) vs 71% (95% CI 63% to 79%), respectively). When ROC-based thresholds were used (calgranulin-C: 0.75 µg/g, calprotectin: 400 µg/g), both tests performed equally well (specificity: 97% (95% CI 94% to 99%) vs 98% (95% CI 95% to 100%)).

CONCLUSIONS

Both calgranulin-C and calprotectin have excellent test characteristics to predict IBD and justify endoscopy.

TRIAL REGISTRATION NUMBER

NCT02197780.

Prospective evaluation of IOTA logistic regression models LR1 and LR2 in comparison with subjective pattern recognition for diagnosis of ovarian cancer in an outpatient setting

OBJECTIVE

To determine whether International Ovarian Tumor Analysis (IOTA) logistic regression models LR1 and LR2 developed for the preoperative diagnosis of ovarian cancer could also be used to differentiate between benign and malignant adnexal tumors in the population of women attending gynecology outpatient clinics.

METHODS

This was a single-center prospective observational study of consecutive women attending our gynecological diagnostic outpatient unit, recruited between May 2009 and January 2012. All the women were first examined by a Level-II ultrasound operator. In those diagnosed with adnexal tumors, the IOTA-LR1/2 protocol was used to evaluate the masses. The LR1 and LR2 models were then used to assess the risk of malignancy. Subsequently, the women were also examined by a Level-III examiner, who used pattern recognition to differentiate between benign and malignant tumors. Women with an ultrasound diagnosis of malignancy were offered surgery, while asymptomatic women with presumed benign lesions were offered conservative management with a minimum follow-up of 12 months. The initial diagnosis was compared with two reference standards: histological findings and/or a comparative assessment of tumor morphology on follow-up ultrasound scans. All women for whom the tumor classification on follow-up changed from benign to malignant were offered surgery.

RESULTS

In the final analysis, 489 women who had either or both of the reference standards were included. Their mean age was 50 years (range, 16-91 years) and 45% were postmenopausal. Of the included women, 342/489 (69.9%) had surgery and 147/489 (30.1%) were managed conservatively. The malignancy rate was 137/489 (28.0%). Overall, sensitivities of LR1 and LR2 for the diagnosis of malignancy were 97.1% (95% CI, 92.7-99.2%) and 94.9% (95% CI, 89.8-97.9%) and specificities were 77.3% (95% CI, 72.5-81.5%) and 76.7% (95% CI, 71.9-81.0%), respectively (P > 0.05). In comparison with pattern recognition (sensitivity 94.2% (95% CI, 88.8-97.4%), specificity 96.3% (95% CI, 93.8-98.0%)), the specificities of the IOTA models were significantly lower (P < 0.0001). A significantly higher number of women would have been offered surgery for suspected cancer if the women had been assessed using the IOTA models instead of pattern recognition (213/489 (43.6%) vs 142/489 (29.0%); P < 0.001).

CONCLUSIONS

The IOTA models maintained their high sensitivity when used in an outpatient setting. Specificity was relatively low, which indicates that a significant proportion of the women would have been offered unnecessary surgery for suspected ovarian cancer. These findings show that the IOTA models could be used as a first-stage test to diagnose ovarian cancer in an outpatient setting, but a different second-stage test is required to minimize the number of false-positive findings. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Feasibility, acceptability and diagnostic test accuracy of frailty screening instruments in community-dwelling older people within the Australian general practice setting: a study protocol for a cross-sectional study

INTRODUCTION

Frailty is one of the most challenging aspects of population ageing due to its association with increased risk of poor health outcomes and quality of life. General practice provides an ideal setting for the prevention and management of frailty via the implementation of preventive measures such as early identification through screening.

METHODS AND ANALYSIS

Our study will evaluate the feasibility, acceptability and diagnostic test accuracy of several screening instruments in diagnosing frailty among community-dwelling Australians aged 75+ years who have recently made an appointment to see their general practitioner (GP). We will recruit 240 participants across 2 general practice sites within South Australia. We will invite eligible patients to participate and consent to the study via mail. Consenting participants will attend a screening appointment to undertake the index tests: 2 self-reported (Reported Edmonton Frail Scale and Kihon Checklist) and 5 (Frail Scale, Groningen Frailty Index, Program on Research for Integrating Services for the Maintenance of Autonomy (PRISMA-7), Edmonton Frail Scale and Gait Speed Test) administered by a practice nurse (a Registered Nurse working in general practice). We will randomise test order to reduce bias. Psychosocial measures will also be collected via questionnaire at the appointment. A blinded researcher will then administer two reference standards (the Frailty Phenotype and Adelaide Frailty Index). We will determine frailty by a cut-point of 3 of 5 criteria for the Phenotype and 9 of 42 items for the AFI. We will determine accuracy by analysis of sensitivity, specificity, predictive values and likelihood ratios. We will assess feasibility and acceptability by: 1) collecting data about the instruments prior to collection; 2) interviewing screeners after data collection; 3) conducting a pilot survey with a 10% sample of participants.

ETHICS AND DISSEMINATION

The Torrens University Higher Research Ethics Committee has approved this study. We will disseminate findings via publication in peer-reviewed journals and presentation at relevant conferences.

Selecting children with suspected inflammatory bowel disease for endoscopy with the calgranulin C or calprotectin stool test: protocol of the CACATU study

INTRODUCTION

The introduction of the faecal calprotectin (FC) test to screen children with chronic gastrointestinal complaints has helped the clinician to decide whether or not to subject the patient to endoscopy. In spite of this, a considerable number of patients without inflammatory bowel disease (IBD) is still scoped. Faecal calgranulin C (S100A12) is a marker of intestinal inflammation that is potentially more specific for IBD than FC, as it is exclusively released by activated granulocytes.

OBJECTIVE

To determine whether the specificity of S100A12 is superior to the specificity of FC without sacrificing sensitivity in patients with suspected IBD.

METHODS

An international prospective cohort of children with suspected IBD will be screened with the existing FC stool test and the new S100A12 stool test. The reference standard (endoscopy with biopsies) will be applied to patients at high risk of IBD, while a secondary reference (clinical follow-up) will be applied to those at low risk of IBD. The differences in specificity and sensitivity between the two markers will be calculated.

ETHICS AND DISSEMINATION

This study is submitted to and approved by the Medical Ethics Review Committee of the University Medical Center Groningen (the Netherlands) and the Antwerp University Hospital (Belgium). The results will be disseminated through a peer-reviewed publication, conference presentation and incorporation in the upcoming National Guideline on Diagnosis and Therapy of IBD in Children.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02197780 .

External Validation of Prediction Models for Pneumonia in Primary Care Patients with Lower Respiratory Tract Infection: An Individual Patient Data Meta-Analysis

Background

Pneumonia remains difficult to diagnose in primary care. Prediction models based on signs and symptoms (S&S) serve to minimize the diagnostic uncertainty. External validation of these models is essential before implementation into routine practice. In this study all published S&S models for prediction of pneumonia in primary care were externally validated in the individual patient data (IPD) of previously performed diagnostic studies.

Methods and Findings

S&S models for diagnosing pneumonia in adults presenting to primary care with lower respiratory tract infection and IPD for validation were identified through a systematical search. Six prediction models and IPD of eight diagnostic studies (N total = 5308, prevalence pneumonia 12%) were included. Models were assessed on discrimination and calibration. Discrimination was measured using the pooled Area Under the Curve (AUC) and delta AUC, representing the performance of an individual model relative to the average dataset performance. Prediction models by van Vugt et al. and Heckerling et al. demonstrated the highest pooled AUC of 0.79 (95% CI 0.74–0.85) and 0.72 (0.68–0.76), respectively. Other models by Diehr et al., Singal et al., Melbye et al., and Hopstaken et al. demonstrated pooled AUCs of 0.65 (0.61–0.68), 0.64 (0.61–0.67), 0.56 (0.49–0.63) and 0.53 (0.5–0.56), respectively. A similar ranking was present based on the delta AUCs of the models. Calibration demonstrated close agreement of observed and predicted probabilities in the models by van Vugt et al. and Singal et al., other models lacked such correspondence. The absence of predictors in the IPD on dataset level hampered a systematical comparison of model performance and could be a limitation to the study.

Conclusions

The model by van Vugt et al. demonstrated the highest discriminative accuracy coupled with reasonable to good calibration across the IPD of different study populations. This model is therefore the main candidate for primary care use.

Anticipating missing reference standard data when planning diagnostic accuracy studies

Results obtained using a reference standard may be missing for some participants in diagnostic accuracy studies. This paper looks at methods for dealing with such missing data when designing or conducting a prospective diagnostic accuracy study

The Value of Repeat Thyroid Fine-Needle Aspiration Biopsy in Patients with a Previously Benign Result: How Often Does It Alter Management?

BACKGROUND

Thyroid nodules are prevalent and mostly benign, being present in up to 67% of the population when assessed by ultrasound. Due to the variable diagnostic performance of ultrasound-guided fine-needle aspiration biopsy (USFNA) of the thyroid and the possibility of a false-negative result, current clinical guidelines recommend ultrasonographic follow-up of benign thyroid nodules. The objective of this study was to evaluate the clinical relevance of a repeat fine-needle aspiration (rFNA) in patients with an initial benign fine-needle aspiration biopsy (iFNA).

METHODS

A retrospective review was conducted of medical records of patients seen at the Mayo Clinic between January of 2003 and December of 2013 who had undergone rFNA of a nodule with benign iFNA. The outcome measured was the result of the rFNA and histopathological correlation, when available.

RESULTS

Three hundred and thirty-four nodules with benign iFNA underwent rFNA during the 10-year study period. The rFNA was most commonly reported as benign (85.3%), followed by suspicious (7.2%), nondiagnostic (5.7%), and malignant (1.8%). The rFNA changed clinical management in 9.5% of the cases. The prevalence of thyroid malignancy ranged from 4.1% to 1.2% based on the gold standard used (histology vs. long-term follow-up, 4.0 ± 2.3 years).

CONCLUSION

In the majority of patients with a benign iFNA, results of the rFNA were unchanged. However, in a small group of patients, the rFNA may differ from the initial results, and alter management. Even so, the prevalence of malignancy remains very low, ranging from 1.2% to 4.1% depending on the gold standard.

Challenges in diagnostic accuracy studies in primary care: the fecal calprotectin example

Background

Low disease prevalence and lack of uniform reference standards in primary care induce methodological challenges for investigating the diagnostic accuracy of a test. We present a study design that copes with these methodological challenges and discuss the methodological implications of our choices, using a quality assessment tool for diagnostic accuracy studies (QUADAS-2).

Design

The study investigates the diagnostic value of fecal calprotectin for detecting inflammatory bowel disease in children presenting with chronic gastrointestinal symptoms in primary care. It is a prospective cohort study including two cohorts of children: one cohort will be recruited in primary care and the other in secondary/tertiary care. Test results of fecal calprotectin will be compared to one of the two reference standards for inflammatory bowel disease: endoscopy with histopathological examination of mucosal biopsies or assessment of clinical symptoms at 1-year follow-up.

Discussion

According to QUADAS-2 the use of two reference standards and the recruitment of patients in two populations may cause differential verification bias and spectrum bias, respectively. The clinical relevance of this potential bias and methods to adjust for this are presented. This study illustrates the importance of awareness of the different kinds of bias that result from choices in the design phase of a diagnostic study in a low prevalence setting. This approach is exemplary for other diagnostic research in primary care.

Understanding the direction of bias in studies of diagnostic test accuracy

Ordering and interpreting diagnostic tests is a critical part of emergency medicine (EM). In evaluating a study of diagnostic test accuracy, emergency physicians (EPs) need to recognize whether the study uses case-control or cross-sectional sampling and account for common biases. The authors group biases in studies of test accuracy into five categories: incorporation bias, partial verification bias, differential verification bias, imperfect gold standard bias, and spectrum bias. Other named biases are either equivalent to these biases or subtypes within these broader categories. The authors go beyond identifying a bias and predict the direction of its effect on sensitivity and specificity, providing numerical examples from published test accuracy studies. Understanding the direction of a bias may permit useful inferences from even a flawed study of test accuracy.

Hysterosalpingosonography for diagnosing tubal occlusion in subfertile women: a systematic review protocol

BACKGROUND

Hysterosalpingosonography has been suggested as a less invasive alternative to hysterosalpingography for detecting tubal occlusion among subfertile women. We aim to determine the diagnostic accuracy of hysterosalpingosonography and to compare it to hysterosalpingography.

METHODS/DESIGN

We will conduct a systematic review of diagnostic test accuracy. We will search Medline, Embase, Cochrane Library, Web of Science and Biosis, as well as reference lists of included studies and previous related review articles. Diagnostic studies that compared hysterosalpingosonography ± hysterosalpingography to laparoscopy with chromotubation in women suffering from subfertility will be eligible. Two authors will independently screen for inclusion, data extraction, and quality assessment. Methodological quality will be assessed using the Quality Assessment of Diagnostic Accuracy Study 2 tool (QUADAS-2). We will use SAS 9.3 (SAS Institute Inc., Cary, NC, USA, 2011) to program bivariate random-effects models, estimate pooled sensitivity and specificity with 95% confidence intervals and to generate summary receiver operating characteristics curves. We will perform sensitivity analyses to examine the effect of differences in techniques used for hysterosalpingosonography and in methodological quality of studies.

DISCUSSION

This systematic review will help to determine if hysterosalpingosonography is an adequate alternative screening test for diagnosing tubal occlusion. Accuracy of specific sono-HSG techniques may also be identified.

TRIAL REGISTRATION

This review has been registered at PROSPERO. The registration number is CRD42013003829.

Quantifying the added value of a diagnostic test or marker

In practice, the diagnostic workup usually starts with a patient with particular symptoms or signs, who is suspected of having a particular target disease. In a sequence of steps, an array of diagnostic information is commonly documented. The diagnostic information conveyed by different results from patient history, physical examination, and subsequent testing is to varying extents overlapping and thus mutually dependent. This implies that the diagnostic potential of a test or biomarker is conditional on the information obtained from previous tests. A key question about the accuracy of a diagnostic test/biomarker is whether that test improves the diagnostic workup beyond already available diagnostic test results. This second report in a series of 4 gives an overview of several methods to quantify the added value of a new diagnostic test or biomarker, including the area under the ROC curve, net reclassification improvement, integrated discrimination improvement, predictiveness curve, and decision curve analysis. Each of these methods is illustrated with the use of empirical data. We reiterate that reporting on the relative increase in discrimination and disease classification is relevant to obtain insight into the incremental value of a diagnostic test or biomarker. We also recommend the use of decision-analytic measures to express the accuracy of an entire diagnostic workup in an informative way.