False Negative Response Rate Research Articles

Comparison of the Performance of a Novel, Smartphone-based, Head-mounted Perimeter (GearVision) With the Humphrey Field Analyzer.

The agreement between a head-mounted perimeter [GearVision (GV)] and Humphrey field analyzer (HFA) for total threshold sensitivity was a mean difference of -1.9 dB (95% limits of agreement -5 to 1). GV was the preferred perimeter in 68.2% of participants. The purpose of this study was to compare reliability indices and threshold sensitivities obtained using a novel, smartphone-based, head-mounted perimeter (GV) with the HFA in normal, glaucoma suspect and glaucoma patients. A secondary objective was to evaluate the subjective experience participants had with both perimeters using a questionnaire. In a prospective, cross-sectional study; 107 eyes (34 glaucoma, 18 glaucoma suspect, and 55 normal) of 54 participants underwent HFA and GV in random order. The main outcome measure was the agreement of threshold sensitivities using Bland and Altman analysis. Participants also completed a questionnaire about their experience with the devices. Median false-positive response rate for GV was 7% (4% to 12%), while for HFA it was 0% (0% to 6%, P<0.001). Median false-negative response rate was similar for both tests. In all, 84 eyes with reliable HFA and GV results were included in the final analysis. Median threshold sensitivity of all 52 points on HFA was 29.1 dB (26.5 to 30.7 dB) and for GV was 30.6 dB (29.1 to 32.6 dB; P<0.001). Mean difference (95% limits of agreement) in total threshold sensitivity between HFA and GV was -1.9 dB (-5 to 1 dB). The 95% limits of agreement were fairly narrow (-8 to 2 dB) across the 6 Garway-Heath sectors. Most participants preferred to perform GV (68.2%) if required to repeat perimetry compared with HFA (20.6%, P<0.001). There was fairly good agreement between the threshold sensitivities of GV and HFA. GV was also preferred by most patients and could potentially supplement HFA as a portable or home perimeter.

Current status and need for standards in ion mobility spectrometry

Ion mobility spectrometry (IMS) is a well established technique for the detection of many compounds of interest based on the reduced mobility (K0) values of their ions. While having the advantage of small size, weight, and power, IMS has been subject to low specificity and is subject to interferences that can cause false alarms in detectors used for security applications. The rate of false positive alarms is directly related to the detection window width required to maintain a high rate of true positive detections. These window widths are in turn a result of the historically available accuracy of reference measurements and the range of responses by multiple detectors. The windows cannot be arbitrarily reduced without risking an increase in the rate of false negative responses. Ongoing work has focused on high accuracy calibration as a means of decreasing the false alarm rates by reducing the variability between detectors which would allow for narrower detection windows. Central to the calibration procedure is the selection of an appropriate calibrant (or reference standard) that can be easily characterized and known with a high degree of certainty across a range of instrumental conditions. This review evaluates a number of previously proposed and potential calibrants against seven recommended criteria of suitability. We examine the sources of false positive alarms in IMS-based detectors and propose a calibration procedure based on high accuracy reference measurements. Initial results of applying this procedure in a post-processing manner are promising towards reducing detector variability and detection window width.

False-Negative Interpretation of Adenocarcinoma In Situ in the College of American Pathologists Gynecologic PAP Education Program.

- Adenocarcinoma in situ (AIS) is difficult to correctly interpret on Papanicolaou (Pap) cytology slides and false-negative interpretations of AIS can cause significant problems in daily practice. - To investigate the false-negative interpretation rate of AIS and the factors related to false-negative interpretation through responses in an educational environment. - We retrospectively evaluated 11 337 responses in the PAP Education Program (PAP-Edu) from 173 AIS slides from 2011 to 2015. The false-negative interpretation rate, most common false-negative interpretations, and related other factors were evaluated. - The overall false-negative rate was 6.9% (784 of 11 337). Respondents correctly interpreted AIS 50.0% (5667 of 11 337) of the time; high-grade intraepithelial lesion (HSIL) and malignancies (adenocarcinoma, squamous cell carcinoma, and other carcinomas) accounted for 42.7% (4842 of 11 337) and low-grade intraepithelial lesion accounted for 0.4% (44 of 11 337) of responses. Overall, 92.7% (10 509 of 11 337) of responses were HSIL and above. Among 784 false-negative responses, negative for intraepithelial lesion or malignancy was the most common (61.5% [482 of 784]), followed by reparative changes (24.1% [189 of 784]) and atrophic vaginitis (7.7% [60 of 784]). Overall, pathologists' responses showed a significantly higher false-negative rate than cytotechnologists' responses (8.3%, 403 of 4835 versus 5.7%, 275 of 4816; P < .001). The false-negative response rates were not statistically different among preparation types. - The low correct interpretation rate and higher false-negative rate for AIS demonstrate the difficulty in interpreting AIS on Pap cytology, which may cause clinical consequences. The higher false-negative rate with pathologists than with cytotechnologists suggests cytotechnologists' higher screening sensitivity for AIS or cautious interpretation to avoid false-positive results by pathologists.

E/N effects on K0 values revealed by high precision measurements under low field conditions.

Ion mobility spectrometry (IMS) is used to detect chemical warfare agents, explosives, and narcotics. While IMS has a low rate of false positives, their occurrence causes the loss of time and money as the alarm is verified. Because numerous variables affect the reduced mobility (K0) of an ion, wide detection windows are required in order to ensure a low false negative response rate. Wide detection windows, however, reduce response selectivity, and interferents with similar K0 values may be mistaken for targeted compounds and trigger a false positive alarm. Detection windows could be narrowed if reference K0 values were accurately known for specific instrumental conditions. Unfortunately, there is a lack of confidence in the literature values due to discrepancies in the reported K0 values and their lack of reported error. This creates the need for the accurate control and measurement of each variable affecting ion mobility, as well as for a central accurate IMS database for reference and calibration. A new ion mobility spectrometer has been built that reduces the error of measurements affecting K0 by an order of magnitude less than ±0.2%. Precise measurements of ±0.002 cm(2) V(-1) s(-1) or better have been produced and, as a result, an unexpected relationship between K0 and the electric field to number density ratio (E/N) has been discovered in which the K0 values of ions decreased as a function of E/N along a second degree polynomial trend line towards an apparent asymptote at approximately 4 Td.

Development and validation of a presumptive color spot test method for the detection of synthetic cathinones in seized illicit materials

Significant quantities of unknown, potentially illicit substances are seized by law enforcement and border protection agencies annually. Color testing is an ideal presumptive test and is commonly employed to provide rapid, selective, inexpensive and simple analyses. Synthetic cathinones are a class of psychoactive substances that do not currently have a suitable, specific color test regularly employed for presumptive identification. Herein, we report on the development and validation of a presumptive color test method employing test reagent, copper(II)-2,9-dimethyl-1,10-phenanthroline (Cu(II)-neocuproine). The procedure is based on the reduction of copper(II) to copper(I) in the presence of the drug, followed by formation of a yellow-orange colored complex with maximum absorbance at 453nm. The simple spot test elicited a positive result for 39 out of 44 cathinone substances tested, which gave a false negative response rate slightly greater than 10%. The structural complexity of cathinone substances, as determined by fractional sp3 (Fsp3) values, were able to classify those that failed to react. Other recreational drugs, adulterants and white powders tested afforded a yellow color change in 10 out of 83 substances examined; however, most of these were still distinguishable from a true positive test result. The color test was applied to cathinone samples cut with glucose and caffeine down to 5%g/g purity, as well as commonly found mixtures of synthetic cathinones, with no effect on the positive color change. The highly stable Cu(II)-neocuproine test reagent has potential for use in preliminary screening of unknown samples for cathinones in forensic laboratory testing.

Role of visual field reliability indices in ruling out glaucoma.

Standard automated perimetry is the current criterion standard for assessment of visual field (VF) loss in glaucoma. The 3 commonly used reliability indices to judge the quality of standard automated perimetry results are fixation losses (FLs) and false-positive (FP) and false-negative (FN) response rates. However, the influence of reliability indices, when within the manufacturer-recommended limits, on VF classification has been sparsely studied. To evaluate the role of VF reliability indices in ruling out glaucoma. A cross-sectional study of 291 eyes of 291 participants referred to a tertiary eye care facility by general ophthalmologists. The participants were suspected to have glaucoma based on optic disc appearance, but the eyes were judged to be normal with physiological cupping by glaucoma experts on masked evaluation of optic disc photographs. All participants underwent VF testing with the Swedish interactive threshold algorithm standard 24-2 program. Logistic regression models were used to evaluate the associations between reliability indices and FP classifications on VF testing (glaucoma hemifield test as outside normal limits and pattern standard deviation with P < .05). Median FL, FP, and FN response rates were 7%, 1%, and 2%, respectively. Among the 241 participants with reliable VF results (FL <20% and FP response rate <15%), the VF classification was normal in 188 (78.0%) and glaucoma (FP) in 53 (22.0%). Probability of FP VF classification was associated with FN response rates (odds ratio [OR], 1.36; 95% CI, 1.25-1.48, P < .001) but did not appear to be associated with FLs (OR, 0.96; 95% CI, 0.90-1.03, P = .30) or FP response rates (OR, 0.96; 95% CI, 0.83-1.12, P = .64). Predicted probability of FP VF classification was 9% (95% CI, 6%-14%), 40% (32%-49%), and 82% (68%-91%) at FN response rates of 0%, 8%, and 16%, respectively. This study suggests that FN response rates have an effect on the ability of automated VF assessments to rule out glaucoma. Since FN response rates are ignored by the manufacturer while flagging a test as unreliable, clinicians and researchers may benefit by realizing that FN response rates can lead to FP VF classification, even when their frequencies are small.

Indications for Repeat Diagnostic Medial Branch Nerve Blocks Following a Failed First Medial Branch Nerve Block

No studies have directly measured the false negative rate of medial branch block (MBB) with correlation to medial branch neurotomy (MBN) outcome. We investigated the potential false negative MBB rate and the subsequent MBN outcome on a consecutive audit of all patients undergoing a double MBB protocol. We prospectively collected audit data and retrospectively collected data by phone on 229 consecutive patients undergoing diagnostic MBB. One-hundred-twenty-two patients reporting greater than 50% of subjective pain relief subsequently underwent either MBN or a confirmatory block followed by MBN. A total of 55 patients underwent a second confirmatory MBB and within that group 27.3% (15/55) reported less than 50% relief post initial MBB and 30.9% (17/55) between 50% and 69% relief. We performed an in-depth analysis of these 2 subgroups focusing on the reason a second MBB was performed despite a “negative” or “indeterminant” first MBB. We divided the “negative” responders to the first MBB into those reporting &lt; 50% relief (Group 1) and those reporting between 50% and 69% relief (Group 2). We calculated a potential 46.7% false negative rate in Group 1 and 47.1% false negative in Group 2; however, the false negative results in Group 1 were predominately in those patients reporting delayed relief of pain and those re-blocked greater than 2 years after the first MBB. The success rate in all patients undergoing MBN was 87% compared to the 75% relief in the false negative groups with no statistically significant difference. In summary, the false negative rate for patients reporting less than 50% relief post MBB is probably less than 20% although there is a high “apparent negative” responds in patients reporting delayed relief or in those who had a second block 2 or more years post initial MBB. Patients reporting between 50 and 69% pain relief have a false negative response rate of 47.1% and should be considered for a confirmatory block. Key words: Facet rhizotomy, zygapophyseal joint, low back pain, chronic pain, facet joint, radiofrequency neurotomy, medial branch block, medial branch neurotomy

The Sensitivity of Motor Response to Needle Nerve Stimulation During Ultrasound Guided Interscalene Catheter Placement

Neurostimulation during single shot interscalene block has a significant false negative motor response rate. Compared with tangential needle approaches for single shot block, interscalene catheter (ISC) placement commonly involves Tuohy needles inserted longitudinally to the brachial plexus. This study aimed to determine the sensitivity of neurostimulation during ultrasound-guided ISC needle placement, and the feasibility of an ultrasound-guided ISC needle endpoint. One hundred fifty-five consecutive nonstimulating ISCs were placed with the needle tip position confirmed by the sonographic spread of 5 mL dextrose 5%. Catheter advancement was then blind 2 to 3 cm past the needle tip. A 0.8 mA electrical stimulus at 2 Hz was applied throughout. When a satisfactory image was obtained, neurostimulation was ignored and the minimum motor response amplitude noted. If imaging was equivocal, a brief appropriate motor response at 0.8 mA was sought. A sustained response at <0.5 mA was only sought if imaging was suboptimal. Prior to surgery conducted under general anesthesia, 30 mL ropivacaine 0.5% was administered through the ISC. Catheter success was defined as a recovery room numerical rating pain score of </=2 (scale, 0-10). In 57% of patients, a muscle response was not elicited. An ultrasound needle endpoint was used in 92% of ISC placements, of which 96% were successful. Sustained twitches at <0.5 mA were obtained in 12 (8%) patients, 6 (4%) of these deliberately sought because of suboptimal imaging. Catheter success overall was 95%. This study suggests that the false negative motor response rate for longitudinal ISC needle placement is higher than the false negative response rate associated with tangential needle approach interscalene block. An ultrasound guided ISC needle endpoint is a feasible alternative to a neurostimulation endpoint.

The Centre for Addiction and Mental Health Concurrent Disorders Screener

To review the characteristics of psychiatric screening tools currently available in addiction treatment services for rapid assessment of comorbid pathology and to introduce the Centre for Addictions and Mental Health Concurrent Disorders Screener (CAMH-CDS), a computer-administered questionnaire that screens for the occurrence of 11 Axis I disorders plus all substance use disorders, as well as for a history of conduct disorder. We describe the structure, contents, and application of the CAMH-CDS. We undertook a sensitivity and specificity trial involving 171 subjects, a test-retest reliability study with 301 participants, and an open-label concordance study with 656 respondents. All subjects were regular clients of a major addiction treatment facility. The CAMH-CDS was easily and effectively used by addiction counsellors with limited or no mental health training. It has a low rate of false-negative responses, and it yields excellent test-retest reliability figures. It is highly sensitive to identifying persons with psychiatric disturbances; however, its ability to discriminate among specific disorders appears to be more limited. The CAMH-CDS can be reliably used to rule out the presence of psychiatric comorbidity in addiction service populations. As with other psychiatric screening instruments, its sensitivity values are stronger than its specificity values. The use of nonstructured clinical evaluations as the gold standard for diagnosis and a likely variance in the patients' symptom reports between the 2 examinations may have contributed to the latter finding.

False-negative responses in primary open-angle glaucoma

To determine the false-negative response rate in patients with primary open-angle glaucoma (POAG) and its relationship with the mean deviation, we evaluated 286 visual fields of patients with POAG. A high false-negative response rate was found in glaucomatous patients compared with healthy controls. When the mean derivation was compared with the false-negative response rate, a logarithmic correlation was found with Pearson correlation analysis.

Does visual sensitivity improve between 5 and 8 years? A study of automated visual field examination

In 74 normal subjects (62 children aged 5–8 years and 12 adults), we tested the widely-held belief that visual sensitivity improves substantially during childhood. Maturation of the retino-striate pathways is generally invoked to account for age-related changes in visual sensitivity. We evaluated the extent to which attentional factors unduly emphasized the effect of age on the purely physiological mechanisms. After a specially-designed familiarization procedure, sensitivity was fully evaluated at two locations in the superior temporal field using a bracketing technique (Octopus 2000R). False-positive (FP) and false-negative (FN) catch-trials were interspersed with the sequence of stimuli. Analyses demonstrated that: (1) age affected sensitivity; and (2) the general level of attentiveness varied not only with age, but also among subjects in the same age group. We then estimated the extent to which improved visual sensitivity may reflect a concomitant evolution of vigilance. Firstly, controlled variance analyses indicated that factors for evaluating attentiveness (rate of FN responses, slope of the psychometric function at the median, and goodness of fit) were indeed much better predictors than age of the sensitivity measured. Secondly and more significantly, the grouping of subjects into homogeneous subgroups, on the basis of their attentional performance, showed that children as young as 5 years may have a visual sensitivity that is only marginally lower than that of adults.

Spatial frequency dependent observer bias in the measurement of contrast sensitivity

A previously reported spatial frequency dependent change in contrast sensitivity, apparently produced by the psychometric method used, was investigated in two experiments. A relative reduction in the measured contrast sensitivity function at higher spatial frequencies was found when using a simple single staircase procedure, even when all external characteristics of the presentation procedure were the same as a more sophisticated and more reliable psychometric method (adaptive probit estimation). The estimated false-negative response rate was found to be greater for the single staircase procedure and was greater at a higher spatial frequency, while the false-positive response rate to interleaved blank presentations did not vary between spatial frequencies and between the two psychometric methods. This supports the suggestion that some subjects, given a knowledge of the psychometric method controlling grating contrast, may adopt different decision criteria at different spatial frequencies.

Evaluation of the tourniquet test as a predictor of diabetic retinopathy

Medical practitioners often have difficulty in assessing the presence or severity of diabetic retinopathy. The tourniquet test is a method of assessing diabetic capillary fragility that has been felt to reliably correlate with background and proliferative diabetic retinopathy. We studied 100 consecutive diabetic patients and 50 age-matched controls in a masked fashion, using fundus photographs and fluorescein angiography to correlate the amount of capillary fragility with the presence and severity of background and proliferative diabetic retinopathy. Although the severity of diabetic capillary fragility did correlate with the presence and severity of diabetic retinopathy ( p < 0.001), this test was not as good an indicator of diabetic retinopathy as were other risk factors such as duration of diabetes ( p ⪡ 0.001). The tourniquet test is unreliable in predicting the presence or severity of diabetic retinopathy because of its high false negative response rate.

Screening for Glaucomatous Visual Field Loss: The Effect of Patient Reliability

Eighty-eight glaucoma patients and 252 normal subjects underwent C-30-2 testing on the Humphrey Field Analyzer. The effect of fixation losses, high false-positive and false-negative response rates on visual field test results was assessed using the mirror image method of detecting asymmetry across the horizontal meridian, and the Humphrey STATPAC pattern standard deviation (PSD) and mean deviation (MD). Glaucoma patients with poor fixation (≥20%) had less depressed fields and fewer localized defects than those with good fixation. Fixation loss did not affect measures of localized defects or generalized depression among normal subjects. High false-positive rates (≥10%) were associated with less-depressed visual fields among glaucoma patients and normal subjects. Visual fields were depressed by an average of 9 dB for glaucoma patients and 7 dB for normal subjects with high false-negative rates (≥33%), when compared with those with low false-negative rates. Apparent localized defects were observed among normal subjects with high false-negative rates. Most of these defects were located in the superior nasal and adjacent arcuate area.

Reliability indexes of automated perimetric tests.

The "reliability" of a subject's automated perimetric test result is generally assessed by three measures: fixation loss and false-positive and false-negative rates. These reliability criteria were examined for 76 glaucomatous and 248 normal subjects who underwent visual field testing (C-30-2 program; Humphrey Visual Field Analyzer, Allergan Humphrey, San Leandro, Calif). Of the examination results, 45% in glaucomatous subjects and 30% in normal controls were considered unreliable with the use of the manufacturer's reliability criteria. Most test results were unreliable because they failed to meet the criterion for fixation loss. The greater rejection rate among glaucomatous subjects was entirely due to their higher rate of false-negative responses. Factors such as age, pupil diameter, and visual acuity did not explain the difference between the false-negative rates of glaucomatous patients and normal subjects.

Large-Image Intensifier Photofluorography and Conventional Radiography in Pulmonary Emphysema

Large-screen image intensifier (II) photofluorography was compared with full-size screen-film chest radiography in the diagnosis of pulmonary emphysema in 84 patients. Photospot films and conventional radiographs were interpreted independently by three radiologists. Computed tomography (CT) was used as an independent reference technique, and diagnostic performance of chest radiography in various CT patterns of emphysema was evaluated. The difference in diagnostic sensitivity for emphysema in favor of conventional chest radiography over photofluorography (0.65 versus 0.56) was statistically significant (p less than 0.05). Specificity of the imaging modalities was equal: 0.78 in full-size films and 0.77 in photospot films. All CT patterns of emphysema had great false negative response rates in chest radiography, which is an inaccurate technique for the diagnosis of emphysema. CT is required for reliable radiologic evaluation of emphysema.

False-negative response rate in epidemiologic studies to define prevalence ratios of epilepsy.

This study has adopted a tested questionnaire, used in a population prevalence study, and distributed it to a sample of people identified as having epilepsy to determine the false-negative response rate for this type of epidemiologic study.

The "false negative" treadmill exercise test and left ventricular dysfunction.

One hundred and fifteen consecutive symptomatic patients undergoing graded exercise testing, selective coronary angiography and left ventriculography were retrospectively evaluated. The sensitivity, specificity, and false negative response rates of the exercise tests were 79%, 81%, and 21%, respectively. Although the magnitude of a positive ST-segment response was related to more extensive vascular disease, the frequency of false negative responses was nearly identical in patients with single, double, or triple vessel disease (22%, 21%, 19%). Analysis of the false negative group demonstrated significant ventriculographic and hemodynamic abnormalities when compared to the true positive responders. Five out of six patients with the most serious motion disorders in the study fell into the false negative group. There were no significant differences in the extent, distribution and severity of vascular involvement, or in the development of collateral circulation in the two groups. However, occluded vessels supplied abnormal ventricular segments more frequently in the false negative group (88% vs 38%); the absence of an "ischemic response" and the presence of segments of abnormal myocardium may be related. Left ventricular dysfunction appears to be an important reason for a false negative response to exercise.

Epilepsy in rural Kentucky: prevalence in a population of school age children.

Seizure prevalence among school age children residing in a rural western Kentucky area (Hardin County) was determined utilizing a method designed to minimize false positives and to allow estimation of false negatives. The observed prevalence of epilepsy is 5.7/1,000 and of febrile seizures 17/1,000. Because of the high rate of false negative responses detected by random sample interview, the true rate of febrile seizures is believed to be closer to a projected rate of 31/1,000.