Proportion Of False-positive Cases Research Articles

An assessment of public health surveillance of Zika virus infection and potentially associated outcomes in Latin America

BackgroundWe evaluated whether outbreaks of Zika virus (ZIKV) infection, newborn microcephaly, and Guillain-Barré syndrome (GBS) in Latin America may be detected through current surveillance systems, and how cases detected through surveillance may increase health care burden.MethodsWe estimated the sensitivity and specificity of surveillance case definitions using published data. We assumed a 10% ZIKV infection risk during a non-outbreak period and hypothetical increases in risk during an outbreak period. We used sensitivity and specificity estimates to correct for non-differential misclassification, and calculated a misclassification-corrected relative risk comparing both periods. To identify the smallest hypothetical increase in risk resulting in a detectable outbreak we compared the misclassification-corrected relative risk to the relative risk corresponding to the upper limit of the endemic channel (mean + 2 SD). We also estimated the proportion of false positive cases detected during the outbreak. We followed the same approach for microcephaly and GBS, but assumed the risk of ZIKV infection doubled during the outbreak, and ZIKV infection increased the risk of both diseases.ResultsZIKV infection outbreaks were not detectable through non-serological surveillance. Outbreaks were detectable through serologic surveillance if infection risk increased by at least 10%, but more than 50% of all cases were false positive. Outbreaks of severe microcephaly were detected if ZIKV infection increased prevalence of this condition by at least 24.0 times. When ZIKV infection did not increase the prevalence of severe microcephaly, 34.7 to 82.5% of all cases were false positive, depending on diagnostic accuracy. GBS outbreaks were detected if ZIKV infection increased the GBS risk by at least seven times. For optimal GBS diagnosis accuracy, the proportion of false positive cases ranged from 29 to 54% and from 45 to 56% depending on the incidence of GBS mimics.ConclusionsCurrent surveillance systems have a low probability of detecting outbreaks of ZIKV infection, severe microcephaly, and GBS, and could result in significant increases in health care burden, due to the detection of large numbers of false positive cases. In view of these limitations, Latin American countries should consider alternative options for surveillance.

Commentary on: Are we overpathologizing everyday life? A tenable blueprint for behavioral addiction research. The diagnostic pitfalls of surveys: If you score positive on a test of addiction, you still have a good chance not to be addicted.

Background and AimsSurvey-based studies often fail to take into account the predictive value of a test, in other words, the probability of a person having (or not having) the disease when scoring positive (or negative) on the given screening test.MethodsWe re-visited the theory and basic calculations of diagnostic accuracy.ResultsIn general, the lower the prevalence the worse the predictive value is. When the disorder is relatively rare, a positive test finding is typically not useful in confirming its presence given the high proportion of false positive cases. For example, using the Compulsive Buying Scale (Faber & O’Guinn, 1992) three in four people classified as having compulsive buying disorder will in fact not have the disorder.ConclusionsScreening tests are limited to serve as an early detection “gate” and only clinical (interview-based) studies are suitable to claim that a certain behaviour is truly “pathological”.

Added value of one-view breast tomosynthesis combined with digital mammography according to reader experience

PurposeTo retrospectively evaluate the added value of one-view breast tomosynthesis in adjunct with mammography to characterize breast lesions. Materials and methodsOur institutional ethics committees approved the study and granted a waiver of informed consent. One hundred fifty-five women (mean age, 51.3 years, range: 24–92 years) who systematically underwent mammography and breast tomosynthesis with subsequent percutaneous biopsy were analyzed. Four radiologists (two seniors, R1 and R2, and two juniors, R3 and R4 with 30, 10, 3 and 1 years of experience in breast imaging, respectively) independently reviewed exams in two steps: mammography alone and tomosynthesis in adjunct with mammography. The lesions in the cohort included 39.3% (61/155) cancers, 2.5% (4/155) high-risk lesions and 58.1% (90/155) benign lesions. A receiver operating characteristic (ROC) curve analysis was performed to compare the results of the two readings. ResultsThere was almost perfect agreement irrespective of reader experience for the reading of the mammography in adjunct with tomosynthesis, whereas agreement was poor between junior and senior readers for the reading of mammography alone. Area under the ROC (Az) values for the tomosynthesis in adjunct with mammography were significantly better than Az values for mammography alone for all readers except the most experienced, for whom only a tendency was noted. The proportion of cancers undiagnosed by mammography alone that were well diagnosed by tomosynthesis in adjunct with mammography was 6.5% (4/61), 13.1% (8/61), 27.8% (17/61) and 26.2% (16/61) for Readers 1, 2, 3 and 4, respectively. The proportion of false positive cases induced by the addition of breast tomosynthesis to mammography was 2.1% (2/94), 2.1% (2/94), 9.5% (9/94) and 12.7% (12/94) for Readers 1, 2, 3 and 4, respectively. ConclusionAdding breast tomosynthesis to mammography improved sensitivity and negative predictive value for all readers except for the most experienced one, in whom only a tendency for improvement was noted.

The relationship between chronic volume overload and elevated blood pressure in hemodialysis patients: use of bioimpedance provides a different perspective from echocardiography and biomarker methodologies

Chronic volume overload is very frequent in hemodialysis (HD) patients and is directly associated with hypertension, increased arterial stiffness, left ventricular hypertrophy (LVH), heart failure and ultimately with higher mortality and morbidity. One major issue is that presently there are very few comparative studies of the various methods (clinical, bioimpedance, inferior cava vein diameter (ICV) and Brain Natriuretic Peptide (NT-proBNP)) for volume status evaluation and their correlation with cardiovascular disease. In 160 patients treated by chronic HD in our center, euvolemic according to clinical assessment, we performed evaluation of volume status through bioimpedance spectroscopy (BIS), ICV and NT-proBNP, as well as echocardiography, to estimate the left ventricle structure and function. Despite appearing clinically euvolemic, severe fluid overload, as defined by a relative tissue hydration (RTH)--i.e. fluid overload over extracellular water ratio (FO/ECW)--above 15% was found in 25.6% of patients. Four categories of patients were considered according to pre-HD BP and BIS values. Forty-five percent of patients (group A) had a reasonable control of BP and volume (SBP < 150 mmHg and RTH < 15%), 29.3% (group B) were classified as hypertensive (SBP > 150 mmHg and RTH < 15%), 16.7% (group C) had high blood pressure and marked volume expansion, (SBP > 150 mmHg and RTH > 15%), while 9% (group D) had SBP < 150 mmHg despite RTH > 15%. Assuming that BIS is the most accurate and validated method to assess hydration status, we calculated the positive predictive value for ICV-based evaluation--18%, with a sensitivity of 67% and an important proportion of false negative cases (45%). NT-proBNP was even less accurate: PPV of only 26%, with a sensitivity of 60% and a specificity of only 45% and an extremely high proportion of false positive cases (73%). Group A patients had the best cardio-vascular profile: lowest LV mass and NT-proBNP levels. Using multi-frequency body impedance spectroscopy, we found a large group of hypertensive and/or fluid-overloaded patients despite apparently being at "dry weight" on clinical evaluation and a marked discrepancy between clinical appearance and fluid status. Of the 4 different methods, assuming BCM "gold standard", there were major disagreements and discrepancies between the other three methodologies. BCM is a valuable and simple bed-side tool for the correct management of BP and risk stratification in HD patients as it allows for excellent discriminators of more abnormal cardiac and vascular profiles.

Record-linkage and capture–recapture analysis to estimate the incidence and completeness of reporting of tuberculosis in England 1999–2002

In 1999 the Enhanced Tuberculosis Surveillance (ETS) system was introduced in the United Kingdom to strengthen surveillance of tuberculosis (TB). The aim of this study was to assess the use of record-linkage and capture-recapture methodology for estimating the completeness of TB reporting in England between 1999 and 2002. Due to the size of the TB data sources sophisticated record-linkage software was required and the proportion of false-positive cases among unlinked hospital-derived TB records was estimated through a population mixture model. This study showed that record-linkage of TB data sources and cross-validation with additional TB-related datasets improved data quality as well as case ascertainment. Since the introduction of ETS observed completeness of notification in England has increased and the results were consistent with expected levels of under-notification. Completeness of notification estimated by a log-linear capture-recapture model was highly inconsistent with prior estimates and the validity of this methodology was further examined.

Neonatal hip instability: screening with anterior-dynamic ultrasound method.

The anterior-dynamic ultrasound method was used for screening 4,430 children for hip dislocation. The frequency of treatment for unstable hip joints was reduced to 0.18%, having been 1.7% without ultrasound screening. No cases of late-diagnosed dislocation were registered. The sensitivity of the pediatricians' clinical examination screening was low, only 24%. After intensive training over several years and improved clinical examination methods, our five technicians managed to increase the sensitivity to 53%. With clinical examination methods, cases of totally dislocated hips can be difficult to diagnose, and only two of four such hips were clinically diagnosed; the proportion of false-positive cases, 0.7%, was also considerable. The anterior-dynamic ultrasound method could optimize the screening results of many clinics.