Likelihood Ratio For Positive Result Research Articles

Prevalence of visual impairment in patients sustaining proximal hip fracture after a simple fall

According to epidemiological studies, the 30% of aged 75 years and older is having impaired vision and most of the cases these patients are not in contact of the hospital care staff and community eye services. The visual assessment of older people is essential and helps to minimize the issues related to fall that led to critical problem. The proper vision is required for regain independence and improve the patient’s overall wellbeing. This kind of situation is leading the individual to unintentional injury which is higher among the visually impaired people compared to fully sighted population. Moreover, there are two major reasons for visual impairment that are more susceptible.The study aims to analyze the prevalence of visual impairment in patients sustaining proximal hip fracture after a simple fall at SCB Medical College and Hospital, Cuttack, Odisha.The current study has been conducted at SCB Medical College and Hospital, Cuttack, Odisha. All inpatients of the orthopaedic rehabilitation wards were recuperating from the surgical repair of a fractured neck of femur aged 75 years and above. and all the visual impairment assessed at Ophthalmology OPD. Moreover, the investigator has also invited the patients who sustained their fracture after a simple slip, trip and fall. Apart from this, the mental test of these participants was also done to analyze the ability. In this test the score of seven and above was considered for allowing the patients to take part in the study. There was a full ocular examination of anterior and posterior segment performed by the ophthalmologist using the slit-lamp bio microscope and indirect ophthalmoscope.Visual impairment of criteria 1 sensitivity was 93% and specificity was 91%. Moreover, the likelihood ratio of positive results was 11 and negative result was 0.05. For the criteria 2 the sensitivity was 97% and specificity was 86%. Moreover, the likelihood of positive results was 6 and negative result was 0.02. Apart from this detection of potentially remedial visual impairment sensitivity was 69% and specificity was 91%. The likelihood ratio of positive result was 8 and negative result was 0.2.The vision test and proper ocular examination were underestimated the extent of vision impairment in older adults. As per the outcome of the study, the visual impairment is common in elderly patients with a history of falls. Moreover, the study has suggested that to measure the visual acuity of all elderly patients recuperating from a proximal hip fracture after a simple fall.

Diahnostychna y peredbachuvana tsinnist i vidnoshennia pravdopodibnosty zminy pokaznykiv deiakykh laboratornykh syndromiv ta yikh konsteliatsii u khvorykh na tsyroz pechinky z porushenniam mineralnoi shchilnosty kistkovoi tkanyny

Diahnostychna y peredbachuvana tsinnist i vidnoshennia pravdopodibnosty zminy pokaznykiv deiakykh laboratornykh syndromiv ta yikh konsteliatsii u khvorykh na tsyroz pechinky z porushenniam mineralnoi shchilnosty kistkovoi tkanyny

Performance of Fatty Liver Index in Identifying Non-Alcoholic Fatty Liver Disease in Population Studies. A Meta-Analysis.

Background. Fatty liver index (FLI) is a non-invasive tool used to stratify the risk of non-alcoholic fatty liver disease (NAFLD) in population studies; whether it can be used to exclude or diagnose this disorder is unclear. We conducted a meta-analysis to assess the prevalence of NAFLD in each FLI class and the performance of FLI in detecting NAFLD. Methods. Four databases were searched until January 2021 (CRD42021231367). Original articles included were those reporting the performance of FLI and adopting ultrasound, computed tomography, or magnetic resonance as a reference standard. The numbers of subjects with NAFLD in FLI classes <30, 30–60, and ≥60, and the numbers of subjects classified as true/false positive/negative when adopting 30 and 60 as cut-offs were extracted. A random-effects model was used for pooling data. Results. Ten studies were included, evaluating 27,221 subjects without secondary causes of fatty liver disease. The prevalence of NAFLD in the three FLI classes was 14%, 42%, and 67%. Sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratio for positive results, likelihood ratio for negative results, and diagnostic odds ratio were 81%, 65%, 53%, 84%, 2.3, 0.3, and 7.8 for the lower cut-off and 44%, 90%, 67%, 76%, 4.3, 0.6, and 7.3 for the higher cut-off, respectively. A similar performance was generally found in studies adopting ultrasound versus other imaging modalities. Conclusions. FLI showed an adequate performance in stratifying the risk of NAFLD. However, it showed only weak evidence of a discriminatory performance in excluding or diagnosing this disorder.

Predictors of vertigo in the emergency department: The preved study

Background and PurposeAcute vertigo (sense of motion) can be the sole manifestation of a posterior circulation stroke, and often gets missed in the emergency department (ED). The studies for evaluation of central vertigo have focused on physical exam findings, which require expertise and may not be suitable for rapid triage by a nurse in ED or by paramedics. MethodsThis cross sectional study included retrospective chart review of patients 18 years of age and older who presented to the Adult ED with acute dizziness or vertigo during the calendar year 2017. All the patients with a diagnosis of central or peripheral vertigo were included in the final analysis. Sensitivity, specificity, Likelihood Ratio of positive result (LR (+)) and Likelihood Ratio of negative result (LR (-)) for central and peripheral vertigo were calculated for risk factors, symptoms and physical examination features. Chi-squared test and univariate logistic regression were used to evaluate statistical correlation and to calculate the prevalence odds ratio (POR). ResultsTwo hundred and forty nine out of 505 (49.3%) patients presenting with dizziness had vertigo. Of these, 14 had central vertigo and 163 had peripheral vertigo. Statistically significant variables were: constant symptoms of vertigo (p 0.000- POR 8.7, 95% confidence interval (CI) 2.3-33.1), no change in symptoms with head movement (p 0.000- POR 10.2, 95% CI 3.0-35.4), dysmetria (p 0.000- POR 56.8, 95% CI 5.8-557.1), and unsteady gait (p 0.000- POR 13.3, 95% CI 3.3-54.3). The sensitivity and specificity to detect central vertigo were 100% and 66.4% respectively if the patient had either unsteady gait, constant symptoms, or no change in symptoms with head movement, [VAIN triad (Vertigo- Ataxia, Incessant, or Non-positional)]. ConclusionsWe suggest that triage with VAIN triad can be used to design prospective studies to develop a triage algorithm for the detection of central vertigo in the ED.

The Diagnostic Accuracy of Сoronary Сomputed Tomography Angiography in the Diagnosis of Stable Coronary Artery Disease in Patients Aged 70 Years and Older

The purpose of this study was to evaluate the diagnostic accuracy of сoronary сomputed tomography angiography (CCTA) in the diagnosis of stable coronary artery disease (CAD) in patients aged ≥70 years. The study included 390 patients aged ≥70 years with symptoms suggested stable CAD which underwent elective coronary artery angiography (CAG). Initially the prevalence of angiographically significant CAD was estimated according to the gender and chest pain character, and identifications of patients in whom CCTA was appropriate. After that diagnostic accuracy and сost-efficiency of CCTA in the diagnosis of stable CAD in 82 patients with atypical angina and non-anginal chest pain were evaluated. The prevalence of obstructive CAD in patients with typical angina was very high and they were excluded from the final analysis. Among 82 patients with atypical angina and non-anginal pain which underwent CCTA 48 (59%) patients had obstructive CAD. CСTA data matched with results of CAG in all cases. Among 34 patients that had non-obstructive CAD the results of CCTA and CAG matched in 88% cases. CCTA has sensitivity, specificity, positive predictive value, negative predictive value of 100%, 88%, 92% and 100% respectively. The likelihood ratio for positive result was 8.3, likelihood ratio for negative result was 0.3. Positive result increased post-test probabilityof obstructive CAD from 42% to 86%, negative result reduced post-test probabilityof obstructive CAD to 0%. negative CCTA result in patients aged 70 years and older with atypical angina and non-anginal pain allows to exclude the presence of obstructive CAD. The likelihood ratio for positive result indicates a moderately difference between the pre-test and post-test probability of the presence of obstructive CAD. In patients aged ≥70 years with atypical angina or non-anginal chest pain which have inconclusive results of functional testing or unable undergo functional testing CCTA allows to increase diagnostic yield of CAG and reduce the frequency of minor complications and diagnostic evaluation costs.

Monitoring Disease Activity in Systemic Lupus Erythematosus With Single-Molecule Array Digital Enzyme-Linked Immunosorbent Assay Quantification of Serum Interferon-α.

No simple or standardized assay is available to quantify interferon-α (IFNα) in routine clinical practice. Single-molecule array (Simoa) digital enzyme-linked immunosorbent assay (ELISA) technology enables direct IFNα quantification at attomolar (femtogram per milliliter [fg/ml]) concentrations. This study was undertaken to assess IFNα digital ELISA diagnostic performances to monitor systemic lupus erythematosus (SLE) activity. IFNα concentrations in serum samples from 150 consecutive SLE patients in a cross-sectional study were determined with digital ELISA and a functional biologic activity assay (bioassay). According to their Safety of Estrogens in Lupus Erythematosus National Assessment version of the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) flare composite scores, patients were divided into groups with inactive SLE (SLEDAI score of <4 or clinical SLEDAI score of 0) or active SLE (SLEDAI score of ≥4 or clinical SLEDAI score of >0), and into groups with no flare or mild/moderate flare or severe flare. Based on serum samples from healthy blood donors, the abnormal serum IFNα level threshold value was 136 fg/ml. Next, using receiver operating characteristic curves for an SLE patient series that was widely heterogeneous in terms of disease activity and organ involvement, the threshold IFNα value associated with active disease was determined to be 266 fg/ml. The digital ELISA-assessed serum IFNα level was a better biomarker of disease activity than the Farr assay because its specificity, likelihood ratio for positive results, and positive predictive value better discerned active SLE or flare from inactive disease. The digital ELISA was more sensitive than the bioassay for detecting low-abnormal serum IFNα concentrations and identifying patients with low disease activity. Direct serum IFNα determination with a highly sensitive assay might improve monitoring of clinical SLE activity and selection of the best candidates for anti-IFNα treatment.

Screening of Extended-Spectrum β-Lactamases (ESBL)-producing Klebsiella pneumoniae with ChromID ESBL Media

BACKGROUND: Klepsiella pneumoniae, one of clinical isolates, is frequently found causative agent of hospital acquired infection. Currently, K. pneumoniae is found as extended-Spectrum β-lactamases (ESBL) producer, allowing it to become multidrugresistant. A clinical laboratory with limited facility needs a valid, reliable, inexpensive and simple laboratory test to control its infection and antimicrobial-resistancy. The aim of this study is to evaluate the diagnostic performance of a ESBL media to detect ESBL-producing K. pneumoniae.METHODS: An independent and blind comparative study of ChromID ESBL media and Double Disc Synergy Test (DDST) was conducted for detecting the clinical isolate of ESBL-producing K. pneumoniae. Clinical isolates of K. pneumoniae collected from the Clinical Laboratory of Dr. Sardjito Hospital were isolated.RESULTS: There were 103 clinical isolates of K. pneumoniae, which were isolated from urine, pus, blood, stool, cerebrospinal fluid, sputum, drain liquid, nasal sinus liquid, gastric wash, bronchi liquid, injury liquid and nasal swab. The number of true positive, true negative, false positive and false negative results were 74, 18, 9 and 2, respectively. Meanwhile, the sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratio for positive result and likelihood ratio for negative result of the new ESBL media were 97.4%, 66.7%, 89.2%, 90%, 2.9 and 0.03, respectively.CONCLUSION: Since the new ESBL media and DDST results were similar, so the new ESBL media could be used for screening patients with clinical presentation that indicating a high suspicious of ESBL-producing bacteria.KEYWORDS: K. pneumoniae, ChromID ESBL, DDST, ESBL, sensitivity

Clinical value of multiplex immune assay of antinuclear antibodies in systemic lupus erythematosus.

A promising trend in the diagnosis of systemic autoimmune diseases is the multiplex immune assay (MIA) of autoantibodies and other laboratory biomarkers using microchips. The aim of the work was to study the diagnostic and prognostic significance of MIA antinuclear antibody (ANA) profiles in systemic lupus erythematosus (SLE). 94 patients with SLE, 70 patients with other rheumatic diseases and 30 healthy donors were examined. ANA (antibodies to doublestranded - dsDNA, Sm, SS-A/Ro, SS-B/La antigens, nucleosomes, ribosomal protein P-RibP and ribonucleoprotein - RNP-70) were determined in the serum by MIA using the xMAP technology. In MIA, antibodies to dsDNA, Sm and RibP have a high diagnostic specificity (Sp) (95.0-99.0%) and a likelihood ratio of positive results (LR+) (9.67-15.0), i.e. are the most "useful" diagnostic tests, and antibodies to RNP-70, SS-A/Ro and nucleosomes are classified as "useful" tests for the diagnosis of SLE (Sp: 84.0-95.0%, LR+> 2.0). Determination of profiles from 3 or more antigen-specific ANA by MIA increases the Sp method to 98.0-100%, and the LR+ - to the maximum values. Profiles from 7 subpopulations of ANA (antibodies to dsDNA, Sm, RibP, SS-A/Ro,SS-B/La, nucleosomes and RNP-70, 57.9%, 71.9%, 82.5%, 61.4 %, 84.2%, 50.9%, 84.2%) were found in the chronic variant of SLE. In the acute course of the disease, 4 subpopulations of ANA are simultaneously detected (antibodies to dsDNA, Sm, SS-A/Ro and nucleosomes, 77.3%, 45.5%, 40.9% and 72.7%); in subacute course there are 2 subpopulations of ANA (antibodies to dsDNA and nucleosomes, 53.3% and 46.7%). The activity index of SLEDAI-2K positively correlates with the concentration of antibodies to dsDNA (r = 0.55, p < 0.05), nucleosomes (r = 0.65, p < 0.05), RibP (r = 0.32; p < 0.05) and Sm (r = 0.36, p < 0.05) in the blood. There was no reliable relationship between the production of varieties of ANA and the index of organ damage. Mucocutaneous disorders, lupus-nephritis and neurolupus were most often associated with the detection of antibodies to dsDNA (53.2-64.0%), nucleosomes (55.3-66.0%), SS-A/Ro (38.0-40.4%) and Sm (27.8-36.2%). MIA of ANA profiles is an important tool for implementing a personalized approach to diagnosis, evaluation of activity, course and clinical and immunologic subtypes of SLE.

Follow-up of recurrences of limb soft tissue sarcomas in patients with localized disease: performance of ultrasound.

To evaluate diagnostic performance of ultrasound in the detection of local recurrences in patients with localized soft tissue sarcomas of the limb. An analysis of patients treated for soft tissue sarcomas between 2005 and April 2014 was performed. Sixty-eight patients (men/women, 36:32; age range, 18-84 years) were evaluated. Sensitivity, specificity with 95% confidence intervals (CIs), positive predictive value (PPV), pre-test probability (the prevalence), negative predictive value (NPV), likelihood ratio for positive results (LH+), accuracy and post-test probability (post-P) of ultrasound were reported on a per patient basis using surgical findings and clinical follow-up as reference standard. Effects of independent variables (US equipment, age and sex, body mass index, radiologist) were considered. Comparison with MR was also performed. The overall sensitivity and specificity were 0.88 (0.60-0.94) and 0.94 (0.86-0.98). PPV, pre-test probability, NPV, LH+, accuracy and post-P: 0.83/0.25/0.96/14.9/0.92/0.83. There were two false negative cases both graded as G3 and deeply located and three false positive US cases. Diagnostic accuracy was not dependent by US machine (p = 0.08), age and sex (p = 0.16), body mass index (p = 0.07) and radiologists (p = 0.07). Diagnostic accuracy of ultrasound was relatively high. Negative US results excluded the presence of a local recurrence with acceptable accuracy. • US accuracy is relatively high in sarcoma follow-up. • Negative US results exclude the presence of local recurrence with acceptable accuracy. • US may miss a small proportion of lesions. • False positive US cases are rare.

Diagnostic performance of ultrasound in patients with suspected brachial plexus lesions in adults: a multicenter retrospective study with MRI, surgical findings and clinical follow-up as reference standard

To evaluate brachial plexus ultrasound (US) performance in a large multicenter study. The research was approved by the Institutional Review Boards, and all patients gave written informed consent. A multicenter retrospective trial including three centers was performed between March, 2006 and April, 2011. A total of 204 patients who received a brachial plexus ultrasound requested by the referring physician were enrolled: magnetic resonance imaging, surgical findings and clinical follow-up of at least 12 months were used as the reference standard. Sensitivity, specificity with 95 % confidence intervals (CIs), positive predictive value (PPV), pre-test-probability (the prevalence), negative predictive value (NPV), pre- and post- test odds (OR), likelihood ratio for positive results (LH+), likelihood ratio for negative results (LH-), accuracy and post-test probability (post-P) were reported on a per-patient basis. The overall sensitivity and specificity with 95 % CIs were: 0.76 (0.75-0.97); 0.96 (0.77-0.89). Overall PPV, pre-test probability, NPV, pre-OR, post-OR, LH+, LH-, Accuracy and post-P were: 0.93/0.43/0.84/0.75/0.75/13.4/17.6/0.25/0.88/0.93, respectively. The specificity of brachial plexus US in patients suspected of having a brachial plexus lesion is very high.

Diagnostic accuracy of MRI in adults with suspect brachial plexus lesions: A multicentre retrospective study with surgical findings and clinical follow-up as reference standard

ObjectiveTo evaluate brachial plexus MRI accuracy with surgical findings and clinical follow-up as reference standard in a large multicentre study. Materials and methodsThe research was approved by the Institutional Review Boards, and all patients provided their written informed consent. A multicentre retrospective trial that included three centres was performed between March 2006 and April 2011. A total of 157 patients (men/women: 81/76; age range, 18–84 years) were evaluated: surgical findings and clinical follow-up of at least 12 months were used as the reference standard. MR imaging was performed with different equipment at 1.5T and 3.0T. The patient group was divided in five subgroups: mass lesion, traumatic injury, entrapment syndromes, post-treatment evaluation, and other.Sensitivity, specificity with 95% confidence intervals (CIs), positive predictive value (PPV), pre-test-probability (the prevalence), negative predictive value (NPV), pre- and post-test odds (OR), likelihood ratio for positive results (LH+), likelihood ratio for negative results (LH−), accuracy and post-test probability (post-P) were reported on a per-patient basis. ResultsThe overall sensitivity and specificity with 95% CIs were: 0.810/0.914; (0.697–0.904). Overall PPV, pre-test probability, NPV, LH+, LH−, and accuracy: 0.823, 0.331, 0.905, 9.432, 0.210, 0.878. ConclusionsThe overall diagnostic accuracy of brachial plexus MRI calculated on a per-patient base is relatively high. The specificity of brachial plexus MRI in patients suspected of having a space-occupying mass is very high. The sensitivity is also high, but there are false-positive interpretations as well.

A rapid immunochromatographic assay for the detection of Mycobacterium tuberculosis antigens in pulmonary samples from HIV seropositive patients and its comparison with conventional methods

As tuberculosis generates a highly heterogeneous antibody repertoire, its diagnosis requires tests based on cocktails of antigens. We describe a new, rapid method called rapid immunochromatographic assay (RICA) for cocktail-based diagnosis, which can detect Mycobacterial antigens in sputum specimens. Six antigenic fractions of pathogenic Mycobacterium tuberculosis were used in combination as the capture antigens in the control line of the flow-through assay. Antigen detection of 200 sputum samples from HIV seropositive patients by RICA assay gave a sensitivity of 97.9%, specificity of 99.0%, positive predictive value of 98.9%, negative predictive value of 98.0%, false positive rate of 0.9%, false negative rate of 2.0%, prevalence rate of 49%, likelihood ratio for positive results 97 and likelihood ratio for negative results 0.02. The combination of RICA and AFB staining gave a sensitivity of 100%, specificity of 100%, positive predictive value of 100%, negative predictive value of 100%, false positive rate of 0%, false negative rate of 0%, likelihood ratio for negative results 0. The assay was simple, rapid and economical for the detection of M. tuberculosis infection and suitable for large scale screening of samples in endemic areas without any sophisticated equipment. The results of the assay proved to be superior to conventional methods and combined with clinical data, could form the basis for starting an earlier course of treatment.

Prediction of successful induction of labor at term: role of clinical history, digital examination, ultrasound assessment of the cervix, and fetal fibronectin assay

Objective The purpose of this study was to evaluate whether biochemical (fetal fibronectin assay) or biophysical (cervical assessment by transvaginal ultrasound) tests may have more value than digital examination in predicting successful induction of labor at term. Study design The study enrolled prospectively 134 women undergoing labor induction at term caused by several obstetric conditions. All participants submitted to digital examination, fetal fibronectin assay, and transvaginal ultrasound for measurement of the cervical length and detection of funneling. The performance of each test in predicting delivery within 24 hours of labor induction was evaluated. Cox multiple regression analysis was performed to identify, among clinical and laboratory tests, which variables were independently associated with the duration of the latent phase and with the total duration of induced labor. Results The likelihood ratios for positive results (predicting that delivery would occur within 24 hours) were 6.61 (95% CI, 1.7-25.8) for a positive obstetric history (previous vaginal delivery), 2.61 (95% CI, 1.6-4.3) for a “favorable” digital examination, 1.41 (95% CI, 0.9-2.2) for a positive fetal fibronectin test, 1.61 (95% CI, 0.9-3.0) for cervical length, and 2.20 (95% CI, 1.1-4.4) for the presence of funneling at transvaginal ultrasound. The likelihood ratios for negative results were 1.81 (1.3-2.5) for obstetric history, 4.34 (2.5-7.7) for digital examination, 1.41 (0.9-2.1) for fetal fibronectin, 1.29 (1.0-1.7) for cervical length, and 1.48 (1.1-2.0) for funneling. On multiple regression, the only variables independently associated with the duration of the latent phase and with the total duration of induced labor were obstetric history and digital examination. Conclusion Only obstetric history and digital examination predicted accurately vaginal delivery within 24 hours and were independently associated with labor duration. Fetal fibronectin and ultrasound measurements failed to predict accurately the outcome of induced labor.

Accuracy of cervicovaginal fetal fibronectin test in predicting risk of spontaneous preterm birth: systematic review

abstractObjective: To determine the accuracy with which a cervicovaginal fetal fibronectin test predicts spontaneous preterm birth in women with or without symptoms of preterm labour.Design: Systematic quantitative review of studies...

Abstracts of Literature.

Abstracts of Literature.

Role of Transcranial Doppler Monitoring in the Diagnosis of Cerebral Vasospasm after Subarachnoid Hemorrhage

OBJECTIVE: The purpose of this study was to determine the correlation between transcranial Doppler (TCD) velocities and angiographic vasospasm after aneurysmal subarachnoid hemorrhage. METHODS: In the first part of this study, patients were retrospectively reviewed to correlate middle cerebral artery absolute blood flow velocities with angiographic vasospasm. In the second part of the study, the middle cerebral artery/ipsilateral extracranial internal carotid artery velocity ratio (Lindegaard ratio) was prospectively correlated with angiographic vasospasm. Angiographic vasospasm was independently graded, by observers blinded to the TCD results, as either none, mild (less than one-third artery luminal narrowing), moderate (one-third to one-half narrowing), or severe (more than one-half narrowing). The sensitivity, specificity, likelihood ratios for positive and negative TCD results, positive and negative predictive values, and kappa and P values were calculated. RESULTS: One hundred one patients were analyzed in the first part of the study, and 44 patients were analyzed in the second part. Interobserver agreement regarding angiographic vasospasm was good (kappa = 0.86). Despite significant correlation between mean velocities and the degree of vasospasm, the clinical dependability of TCD velocities (evaluated using predictive values and likelihood ratios) was limited. The positive predictive value of velocities of > or =200 cm/s for moderate/severe angiographic vasospasm was 87% but that of lower velocities was approximately 50%. The negative predictive value of velocities of <120 cm/s was 94% but that of higher velocities was approximately 75%. Only the likelihood ratios for velocities of <120 or > or =200 cm/s were useful (likelihood ratio for negative result = 0.17, likelihood ratio for positive result = 16.39). Overall, 57% of patients exhibited maximum velocities in the indeterminate range between 120 and 199 cm/s. Lindegaard ratios did not improve the predictive value of TCD monitoring. CONCLUSION: For individual patients, only low or very high middle cerebral artery flow velocities (i.e., <120 or > or =200 cm/s) reliably predicted the absence or presence of clinically significant angiographic vasospasm. Intermediate velocities, which were observed for approximately one-half of the patients, were not dependable and should be interpreted with caution.

Uncertainty in Bayes.

Most standard discussions of Bayes' formula treat sensitivity, specificity, and the prior probability as fixed parameters for probability revision, but in fact these usually have associated variability. This in turn generates predictable patterns of uncertainty in the posterior probabilities. Although these have not been investigated in detail, they have important implications for the interpretation of posterior probabilities and the clinical use of Bayesian probability revision. For a test with a high likelihood ratio for a positive result, the positive predictive value (PPV) is strongly affected by uncertainties in the prior probability when the prior probability is small, but PPV is almost independent of such uncertainties at high values of the prior probability. The PPV is more affected by changes in specificity than by changes in sensitivity, and uncertainty in specificity has its maximal impact on the PPV at low prior probability values. These patterns are most pronounced for tests with high likelihood ratios of positive results. Similar results can be shown for the negative predictive value. These results imply that for suitability good tests, probability revision in certain definable ranges of prior probability may be so strongly affected by errors in the estimations of both the prior probability and the operating characteristics that the posterior probabilities may be unstable in practice. On the other hand, at other values of the prior probability, the posterior probabilities are almost constant, and formal probability revision will not have much impact. These patterns indicate limitations to the reliability and usefulness of calculated posterior probabilities, and have important implications for the clinical use of Bayes' formula.

Diagnostic value of microtympanometry in primary care.

To determine the reliability, validity, and feasibility of a new hand held microtympanometer. Comparison of microtympanometry by two independent observations of a general practitioner and a nurse, and against a validated reference instrument. Primary care health centre of a school for the deaf in the United States. 111 schoolchildren receiving a regular check up. Tympanometry with the Grason Stadler 28, classified with a slightly modified Jerger's classification. Interobserver reliability was 0.95 (Cohen's kappa). Results of microtympanometry were highly comparable with results of the reference instrument (likelihood ratio of positive results, 161.2). The microtympanometer could be used in general practice: it is hand held, child friendly, easy to handle, and accurate.