Significant Decrease In Specificity Research Articles

Evaluation of comprehensive chromosome screening platforms for the detection of mosaic segmental aneuploidy

PurposeA subset of preimplantation embryos identified as euploid may in fact possess both whole and sub-chromosomal mosaicism, raising concerns regarding the predictive value of current comprehensive chromosome screening (CCS) methods utilizing a single biopsy. Current CCS methods may be capable of detecting sub-chromosomal mosaicism in a trophectoderm biopsy by examining intermediate levels of segmental aneuploidy within a biopsy. This study evaluates the sensitivity and specificity of segmental aneuploidy detection by three commercially available CCS platforms utilizing a cell line mixture model of segmental mosaicism in a six-cell trophectoderm biopsy.MethodsTwo cell lines with known karyotypes were obtained and mixed together at specific ratios of six total cells (0:6, 1:5, 2:4, 3:3, 4:2, 5:1, and 6:0). A female cell line containing a 16.2 Mb deletion on chromosome 5 and a male cell line containing a 25.5 Mb deletion on chromosome 4 were used to create mixtures at each level. Six replicates of each mixture were prepared, randomized, and blinded for analysis by one of the three CCS platforms (SNP-array, VeriSeq NGS, or NexCCS). Sensitivity and specificity of segmental aneuploidy at each level of mosaicism was determined and compared between each platform. Additionally, an alternative VeriSeq NGS analysis method utilizing previously published criteria was evaluated.ResultsExamination of the default settings of each platform revealed that the sensitivity was significantly different between NexCCS and SNP up to 50% mosaicism, custom VeriSeq, and SNP-array up to 66% mosaicism, and between NexCCS and custom VeriSeq up to 50% mosaicism. However, no statistical difference was observed in mixtures with >50% mosaicism with any platform. No comparison was made between default VeriSeq, as it does not report segmental imbalances. Furthermore, while the use of previously published criteria for VeriSeq NGS significantly increased sensitivity at low levels of mosaicism, a significant decrease in specificity was observed (66% false positive prediction of segmental aneuploidy).ConclusionThese results demonstrate the potential of NGS-based detection methods to detect segmental mosaicism within a biopsy. However, these data also demonstrate that a balance between sensitivity and specificity should be more carefully considered. These results emphasize the importance of vigorous preclinical evaluation of new testing criteria prior to clinical implementation providing a point of departure for further algorithm development and improved detection of mosaicism within preimplantation embryos.

Sensitive Troponin I Assay in Patients with Chest Pain - Association with Significant Coronary Lesions with or Without Renal Failure.

IntroductionDespite having higher sensitivity as compared to conventional troponins, sensitive troponins have lower specificity, mainly in patients with renal failure.ObjectiveStudy aimed at assessing the sensitive troponin I levels in patients with chest pain, and relating them to the existence of significant coronary lesions.MethodsRetrospective, single-center, observational. This study included 991 patients divided into two groups: with (N = 681) and without (N = 310) significant coronary lesion. For posterior analysis, the patients were divided into two other groups: with (N = 184) and without (N = 807) chronic renal failure. The commercial ADVIA Centaur® TnI-Ultra assay (Siemens Healthcare Diagnostics) was used. The ROC curve analysis was performed to identify the sensitivity and specificity of the best cutoff point of troponin as a discriminator of the probability of significant coronary lesion. The associations were considered significant when p < 0.05.ResultsThe median age was 63 years, and 52% of the patients were of the male sex. The area under the ROC curve between the troponin levels and significant coronary lesions was 0.685 (95% CI: 0.65 - 0.72). In patients with or without renal failure, the areas under the ROC curve were 0.703 (95% CI: 0.66 - 0.74) and 0.608 (95% CI: 0.52 - 0.70), respectively. The best cutoff points to discriminate the presence of significant coronary lesion were: in the general population, 0.605 ng/dL (sensitivity, 63.4%; specificity, 67%); in patients without renal failure, 0.605 ng/dL (sensitivity, 62.7%; specificity, 71%); and in patients with chronic renal failure, 0.515 ng/dL (sensitivity, 80.6%; specificity, 42%).ConclusionIn patients with chest pain, sensitive troponin I showed a good correlation with significant coronary lesions when its level was greater than 0.605 ng/dL. In patients with chronic renal failure, a significant decrease in specificity was observed in the correlation of troponin levels and severe coronary lesions.

Serologic Assay for Diagnosis of Celiac Disease Based on a Patient-Derived Monoclonal Antigliadin Antibody

Patients with celiac disease can be identified based on the detection of serum antibodies to deamidated gliadin peptides (DGPs). Recombinant human monoclonal antibodies (hmAb) against gliadin are produced by cloning antibody genes from single IgA-producing plasma cells isolated from lesions of patients with celiac disease. We developed an assay to identify patients with celiac disease based on the ability of antibodies from their serum to inhibit the binding of a gliadin-specific hmAb (1002-1E03) to a specific peptide antigen (inhibition assay). We selected 2 peptides (a 34-mer and a 26-mer) found in ω-gliadins and low-molecular-weight glutenins that had been identified as specific targets of the hmAb 1002-1E03 from a digest of gliadin treated by transglutaminase 2. These peptides contained repeat sequence motifs; their interaction with hmAb 1002-1E03 was assessed in an amplified luminescent proximity homogeneous inhibition assay. We also tested peptides we created that included 3 repeated sequence motifs. Serum samples from untreated patients diagnosed with celiac disease (n= 106) and 2 control groups (198 blood donors, 151 patients with Crohn's disease) were analyzed using the assay, as well as in conventional commercial assays that measure IgA against transglutaminase 2 (TG2) or IgG against DGP. In our inhibition assays, the 34-mer peptide showed the best results, and identified patients with celiac disease with 86.8% sensitivity and 98.6% specificity. Its diagnostic accuracy was comparable with that of commercial anti-DGP IgG (sensitivity, 87.9%; specificity, 98.0) and anti-TG2 IgA (sensitivity, 81.1%; specificity, 98.9) assays, and it detected most of the patients with anti-TG2 IgA-negative celiac disease without a significant decrease in specificity. Combined use of the anti-ω34 and the anti-TG2 assays produced specificity and sensitivity values of 95.3% and 98.0%, respectively. We developed an antigliadin inhibition assay that identifies patients with celiac disease with high levels of specificity and sensitivity. It may prove useful as an adjunct to the current assay for anti-TG2 IgA.

Improvement in DMSA imaging using adaptive noise reduction

Dimercaptosuccinic acid imaging is the 'gold standard' for the detection of cortical defects and diagnosis of scarring of the kidneys. The Siemens planar processing package, which implements adaptive noise reduction using the Pixon algorithm, is designed to allow a reduction in image noise, enabling improved image quality and reduced acquisition time/injected activity. This study aimed to establish the level of improvement in image quality achievable using this algorithm. Images were acquired of a phantom simulating a single kidney with a range of defects of varying sizes, positions and contrasts. These images were processed using the Pixon processing software and shown to 12 observers (six experienced and six novices) who were asked to rate the images on a six-point scale depending on their confidence that a defect was present. The data were analysed using a receiver operating characteristic approach. Results showed that processed images significantly improved the performance of the experienced observers in terms of their sensitivity and specificity. Although novice observers showed significant increase in sensitivity when using the software, a significant decrease in specificity was also seen. This study concludes that the Pixon software can be used to improve the assessment of cortical defects in dimercaptosuccinic acid imaging by suitably trained observers.

Combination of the PAM4 and CA19-9 biomarkers to improve the detection of pancreatic adenocarcinoma.

164 Background: Pancreatic ductal adenocarcinoma (PDAC) is almost universally lethal, due mainly to the inability to detect early-stage disease. Thus, identification of biomarkers that can identify patients with early-stage PDAC may improve overall survival. Methods: In a blinded study, PAM4 and CA19-9 immunoassays were performed on sera from 480 patients, including those with confirmed PDAC (N=234), other cancers (N=84), benign diseases of the pancreas (N=89), and healthy adults (N=50). Results: Overall sensitivity for PDAC was similar, 74% and 77% for PAM4 and CA19-9, respectively. Sensitivity for detection of early, stage-1 disease (N=26), although somewhat higher for the PAM4-antigen, was also statistically similar, 65% and 58% for PAM4 and CA19-9, respectively (P = 0.5775). However, specificity was significantly lower for CA19-9, particularly with respect to chronic pancreatitis (CP): 68% vs.86% for the PAM4 assay (P = 0.014). Furthermore, CA19-9 results showed considerably higher detection rates for non-PDAC neoplasia, including patients with other cancers that metastasized to the pancreas. Thus, positive likelihood ratios (+LR) were lower for CA19-9 (+LR = 2.41) than for the PAM4 assay (+LR = 5.29). PAM4 and CA19-9 antigen levels in PDAC were independent of each other (r2 = 0.003, P=0.410); however, the positive and negative interpretations were concordant in 68% of the cases. Thus, we used a combined biomarker analysis that ultimately improved the overall PDAC detection rate (84%), without a significant decrease in specificity (83%). Comparison of the ROC curves for PDAC vs. CP and PDAC vs. benign disease demonstrated a statistically significant improvement for the combined immunoassay, as compared to either assay alone (P &lt; 0.0001 in both comparisons), to detect and discriminate PDAC from benign disease. Conclusions: While the PAM4-immunoassay provides high sensitivity and specificity for detection and diagnosis of PDAC, inclusion of the CA19-9 biomarker significantly enhanced positive identification of PDAC patients, from 74% to 84%. Further studies are needed to confirm these results. (Supported in part by NIH grants CA096924, CA120432 and CA62924, and the Turpin Foundation.)

Does power Doppler ultrasonography improve the BI-RADS category assessment and diagnostic accuracy of solid breast lesions?

Power Doppler ultrasonography (US) is used in addition to B-mode US as a tool for the differential diagnosis between benign and malignant lesions. However, there are few data showing how useful power Doppler US is for BI-RADS category assessment. To assess how much power Doppler US contributed to increasing the category diagnosis from Breast Imaging Reporting and Data System (ACR BI-RADS(®)-US) category 3 to category 4. A total of 2426 patients (age range 16-91 years, mean 52 years) who underwent B-mode and power Doppler breast US using a linear 10-MHz transducer were analyzed. We devised integrated US category classification (BI-RADS-Integral) based on BI-RADS descriptors and vascularity. Masses with a circumscribed margin, parallel orientation, and negative vascularity on power Doppler US were defined as category 3. Irregular-shaped masses with a spiculated margin or echogenic halo were defined as category 5. Masses with one of the four suspicious findings (no circumscribed margin, no parallel orientation, microcalcifications, and positive vascularity) were defined as category 4a, and masses with two or more suspicious findings were defined as category 4b. There were 98 breast cancer cases, and the average sizes of invasive and non-invasive cancers were 15 mm and 18 mm, respectively. The frequency of breast cancer according to category was: 0.4% (3/714) of the category 3 cases, 2.7% (7/256) in category 4a, 64% (47/73) in category 4b, and 100% (41/41) in category 5. Among the cases with a category 4a mass lesion, there were 183 lesions whose category diagnosis had been raised from category 3 to category 4a based on the Doppler blood flow findings alone, and 3 (1.6%) of those lesions were breast cancer. All three of them were ductal carcinoma in situ (DCIS) cases. When the cut-off point was placed between category 3 and category 4, BI-RADS-Integral and BI-RADS-US without power Doppler had a sensitivity of 96.9% and 93.9%, respectively, specificity of 72.1% and 90.4%, respectively, and accuracy of 74.4% and 90.7%, respectively. The presence of Doppler blood flow increases the malignancy pick-up rate, but at the expense of a significant decrease in specificity and diagnostic accuracy and an increase in biopsy rate.

Corrected QT dispersion improves diagnostic performance of exercise testing in diagnosing coronary artery disease

To determine the best combination of parameters that would improve the diagnostic performance of exercise testing, coronary angiography plus exercise testing were done on 112 patients with angina pectoris and normal electrocardiogram. The univariate predictors of coronary artery disease included: age > or = 40 years, male sex, hypertension, smoking, development of exertional chest pain, decrease in systolic blood pressure (BP) > or = 10 mmHg or systolic BP 3 min post-exercise > 90% of peak, heart rate drop < 12 beats/min 1 min postexercise, exercise-induced ST-segment depression > or = 1 mm. Multivariate logistic regression analysis showed that using either ST depression > or = 1 mm or peak exercise QTDc > 70 ms significantly improved sensitivity and negative predictive value of the test without a significant decrease in specificity.

Clinical reliability of non‐organoleptic oral malodour measurements

Measurement of volatile sulphur compounds (VSC) by portable sulphur monitors (Halimeter, OralChroma) is a common practice for diagnosis of oral malodour. In this study, the clinical value of these devices was examined. Two hundred and eighty patients with bad breath complaints attending a halitosis consultation were enrolled. Organoleptic scores were given by a trained and calibrated judge, before measurement of the VSC levels (Halimeter, OralChroma), to avoid any bias. Significant correlations were found between the organoleptic assessment, the Halimeter, and the OralChroma (R=0.74 for organoleptic versus Halimeter; 0.66 for organoleptic versus OralChroma; 0.63 for Halimeterversus OralChroma). The sensitivity and specificity (with regard to the organoleptic score) to detect patients with/without oral malodour for the Halimeter were 63% and 98%, respectively, and for the OralChroma 69% and 100% when using the cutoffs suggested by the manufacturer. By lowering these values, sensitivity could be improved without a significant decrease in specificity (both devices). We concluded that the measurement of the VSC levels can be used as an adjunct to the organoleptic assessment. Thresholds should be revisited in order to improve their clinical utility. These devices can prove the absence of malodour in case of pseudo-halitosis.

Encircling reperfusion pattern on the stress-minus-delay bull's-eye map improves sensitivity of myocardial perfusion scans

Myocardial perfusion imaging is subject to considerable noise due to re-registration and attenuation artifact. On a retrospective review, we identified 51 studies that showed encircling reperfusion pattern on a stress-minus-delay bull's-eye map with concurrent cardiac catheterization within 4 months. Encircling reperfusion was defined as a band of reversibility > or =2.5 standard deviations above that of the gender-matched and age-matched normal studies. This had to surround the delay defect for at least two-thirds of its circumference on the stress-minus-delay bull's-eye map. Three expert readers, blinded to cardiac catheterization results, individually interpreted myocardial perfusion imaging without and with a stress-minus-delay bull's-eye map. A certainty index of 1-100 (100 being the highest certainty for the presence of perfusion defects) was recorded for image interpretation. The intra-class correlation coefficient between readers indicated a strong agreement. Using encircling reperfusion pattern on a stress-minus-delay bull's-eye map, the mean increase in certainty index scores was 8.0+/-7.30 (P<0.0001). This increase in certainty index scores was associated with a significant increase in sensitivity from 67 to 83% (P=0.01) without any significant decrease in specificity (P=0.16). The pattern of encircling reperfusion on the stress-minus-delay bull's-eye map can improve the interpreter's confidence and sensitivity without significantly compromising specificity for identifying true myocardial perfusion defects.

Combining Structural and Functional Testing for Detection of Glaucoma

To assess whether the combined use of both structural and functional tests improves discrimination between healthy and glaucomatous eyes over either type of testing alone. Observational cross-sectional study. One hundred twenty-three eyes of 123 participants enrolled in the Diagnostic Innovations in Glaucoma Study. Because both structural and functional tests were evaluated, 2 definitions of glaucoma were used: glaucomatous visual field (VF) damage based on repeatable abnormal standard automated perimetry results (n = 43) and glaucomatous optic disc (glaucomatous optic neuropathy [GON]) based on masked assessment of optic disc stereophotographs (n = 65). Participants had scanning laser polarimetry, optical coherence tomography (OCT), and confocal scanning laser ophthalmoscopy imaging in addition to frequency-doubling technology (FDT) perimetry and short-wavelength automated perimetry (SWAP) testing completed within a 6-month interval. For each glaucoma definition, sensitivities and specificities were calculated for the best structural parameters, FDT perimetry pattern standard deviation (PSD), and SWAP PSD/glaucoma hemifield test, and then for each possible pairwise combination of one structural and one functional parameter. The best structural parameters for discriminating between glaucoma and control eyes were nerve fiber indicator for scanning laser polarimetry, inferior average retinal nerve fiber layer thickness for OCT, and Moorfields regression classification for confocal scanning laser ophthalmoscopy. Sensitivities and specificities for detecting glaucomatous VF damage for scanning laser polarimetry, OCT, confocal scanning laser ophthalmoscopy, FDT perimetry, and SWAP were 41.9% and 98.3%, 58.1% and 98.3%, 58.1% and 84.5%, 44.2% and 98.3%, and 65.1% and 86.2%, respectively. Adding FDT perimetry to each of the best structural parameters led to a significant (P<0.05) increase in sensitivity without a significant change in specificity compared with structural parameters alone. Adding SWAP to each of the best structural parameters led to a significant increase in sensitivity and also a significant decrease in specificity compared with each structural parameter alone. A combination of parameters from structural tests and functional tests can improve the sensitivity of glaucoma detection. The sensitivity and specificity desired for a particular clinical application will determine the selection of the particular diagnostic tests.

Exercise supplementation to dipyridamole prevents hypotension, improves electrocardiogram sensitivity, and increases heart-to-liver activity ratio on Tc-99m sestamibi imaging

Background. Myocardial perfusion imaging with dipyridamole is an alternative with which to evaluate patients who are unable to exercise. Many patients who undergo dipyridamole testing are limited in their ability, but are not completely unable, to exercise. There are benefits from adding low workload exercise to dipyridamole testing, including a reduction of thallium 201 concentration in the liver, leading to a higher heart-to-liver activity ratio and better image quality. This prospective study was designed to evaluate a protocol of exercise supplementation during dipyridamole technetium 99m sestamibi imaging and to verify whether a higher heart-to-liver activity ratio could be obtained. We also evaluated the potential of this combined protocol to prevent hypotension and induce ischemic changes on the electrocardiogram (ECG). Methods and Results. Ninety consecutive patients who were not completely disabled for exercise underwent dipyridamole Tc-99m sestamibi cardiac single photon emission computed tomography with a protocol of exercise supplementation (DipEx). The heart-to-liver activity ratio, hemodynamics, and electrocardiographic changes were studied. The findings were compared with those of a control group (Dip) composed of 99 patients who underwent dipyridamole infusion alone. Patients with left bundle branch block, pacemaker, and atrial fibrillation were excluded. The DipEx patients tolerated the protocol, exercising 4.2 ± 1.3 minutes on the treadmill (Bruce protocol). Compared with Dip, patients in the DipEx group had a higher heart-to-liver activity ratio (1.3 ± 0.4 vs 1.6 ± 0.5, respectively; P = .00001), had no incidence of hypotension (6% vs 0%, respectively; P = .03), and had a higher sensitivity of the ECG to detect ischemia (6% vs 34%, respectively; P = .003). The increase in sensitivity seen in the DipEx group was accompanied by a significant decrease in specificity compared with the Dip group (67% vs 100%, P = .000001). Conclusions. Our data show that the addition of limited exercise to dipyridamole results in benefits during Tc-99m sestamibi imaging, increasing heart-to-liver activity ratio, preventing vasodilator-induced hypotension, and improving ECG sensitivity for the detection of ischemia. Furthermore, this protocol also provides an estimation of the patient's physical capacity and could be used as an alternative for patients undergoing dipyridamole infusion who are not completely unable to exercise. (J Nucl Cardiol 2001;8:652-9.)

Diagnostic ability of general practitioners and dermatologists in discriminating pigmented skin lesions

Background: Early recognition of melanoma is the key in preventing metastatic disease. Objective: The aim of this study was to evaluate diagnostic ability of general practitioners (GPs) and dermatologists concerning pigmented skin lesions in general and melanoma in particular. We also investigated whether the diagnostic ability of GPs changed after a lecture on melanoma. Methods: A test set of 13 pigmented skin lesions on 35-mm color slides was presented to 160 GPs and 60 dermatologists during educational courses. Results: GPs correctly evaluated biologic behavior of the pigmented skin lesions in 72% of the evaluations. In 71% of these evaluations they correctly identified the lesions. The proportion of lesions correctly identified was positively correlated with the frequency of pigmented skin lesions in everyday practice. Dermatologists made a correct identification of the lesions in 88% of all evaluations, and they correctly evaluated biologic behavior in 94% of these. Recognition of melanoma was proportional to melanoma exposure in everyday practice. Thick melanomas were better recognized than thin melanomas in both physician groups. After a lecture on melanoma, sensitivity of GPs to recognize malignant disease increased from 72% to 84%, without a significant decrease in specificity. The proportion of lesions correctly identified also rose significantly (66% vs 52%). (J Am Acad Dermatol 2001;44:979-86.)

Combined Pap Smear, Cervicography and HPV DNA Testing in the Detection of Cervical Intraepithelial Neoplasia and Cancer

The sensitivity of the Pap smear (PAP) continues to be the subject of debate. During the past several years, cervicography (CER) and HPV DNA testing have been suggested as optional tools in the screening of cervical cancer precursors. The performance characteristics of PAP, CER and HPV DNA testing (hybrid capture test [HCT]) in all potential combinations were evaluated in a series of 1,030 women (aged 16-70, median, 33), subjected to colposcopy (COLPO) as the reference tool. Of the 992 evaluable cases, 402/992 (41%) had positive COLPO (i.e., an abnormal transformation zone). Of them, 298 women underwent directed punch biopsy, while of the COLPO negative patients, 18/93 positive by at least one of the three tests had endocervical curettage. Of the 402 COLPO positive women, 146 (36%) remained negative on all tests, whereas 256 (64%) had at least one positive test. There were 84 cervical intraepithelial neoplasia (CIN) 2 and 3 lesions and 6 invasive carcinomas. Of the former, 10 were detected by PAP alone, 4 by CER alone and 3 by HCT alone. Three of the 6 carcinomas were HCT negative. The predictive value (PPV) of a positive test was 45% for PAP, 51% for CER and 48% for HCT. The combinations of PAP with CER (for PAP negative cases) and PAP with HCT were more sensitive for CIN 2 and 3 (95% and 94%, respectively) as compared with PAP alone but were associated with a significant decrease in specificity (44% and 46% vs. 57%, respectively). However, both combinations retained a PPV (43%) similar to that of PAP alone (45%). The potential combinations of PAP with CER and with HCT were more sensitive in detecting CIN 2 and 3 as compared with PAP alone and retained a PPV similar to that of PAP.

CD19 selection improves the sensitivity of B cell lymphoma detection.

Reinfusion of residual tumor cells into B cell non-Hodgkin's lymphoma (B-NHL) patients during autologous transplantation may be an important cause of disease relapse. Determining the extent to which B-NHL cells are present in autologous progenitor cell products and if the presence of residual B-NHL cells is predictive of relapse will require extremely sensitive methods of detecting rare B-NHL cells. We attempted to improve the sensitivity of polymerase chain reaction (PCR)-based detection of rare B-NHL cells by preselecting CD19+ cells using an immunomagnetic column. To measure detection sensitivity, we prepared samples containing different levels of B-NHL cell contamination by mixing B-NHL cell lines containing the chromosomal translocation t(14;18) bcl-2/JH) with control leukapheresis samples. DNA extracted from each CD19-selected sample and from each matched nonselected sample was added to a PCR to amplify the bcl-2/JH breakdown junction. CD19 preselection improved the sensitivity of detection of t(14;18)-positive B-NHL cells 115-fold, so that B-NHL cells at a concentration of 1 tumor cell per 1 x 10(6) hematopoietic cells were detected in every specimen evaluated. t(14;18)-positive cells were not detected in any of 13 control leukapheresis specimens. We conclude that a combination of CD19 preselection and PCR amplification may improve the sensitivity of detection of rare lymphoma cells by two orders of magnitude without a significant decrease in specificity.

Carbon 13–labeled urea breath test for the diagnosis of Helicobacter pylori infection in children

Helicobacter pylori infection is mainly acquired in childhood, and studies on the epidemiology of this infection depend on the availability of a noninvasive diagnostic test for use in children. The aim of this study was to determine whether the carbon 13–labeled urea breath test (UBT) can be used in children by evaluating: (1) its sensitivity and specificity compared with either culture or both rapid urease test and histologic examination, (2) whether a test meal or a prolonged fast is required, (3) the usefulness after treatment for H. pylori. Eighty-eight children (mean age, 10.6 ± 4.19 years) who were undergoing upper endoscopy were studied while fasting, not fasting, and after treatment. Children were given 50 mg of 13C-urea if they weighed less than 50 kg or 75 mg of 13C-urea if they weighed more than 50 kg with 50 mg of a glucose polymer solution in 7.5 ml of water. Breath samples were collected at baseline and at 15, 30, 45, and 60 minutes. In 63 fasting children the UBT was 100% sensitive and 97.6% specific at 30 minutes with a cutoff value of 3.5 d 13 CO 2 per mil. Nonfasting tests in 23 children, performed between 1 and 2 hours after their usual meal, were 100% sensitive and 91.6% specific. In 13 children fed directly before the UBT, the sensitivity of the test was reduced to 50%. Thirty minutes was the optimal sampling time. There was a significant decrease in specificity when samples were obtained at 15 minutes, possibly caused by the interference of oral urease-producing organisms. The test was 100% sensitive and specific in 20 children after treatment for infection. The UBT is a highly sensitive and specific test for the diagnosis of H. pylori infection in children. Neither a prolonged fast nor a test meal is required. (J Pediatr 1997;131:815-20)

Comparison of radioimmunoassay and enzyme immunoassay kits for detection of Legionella pneumophila serogroup 1 antigen in both concentrated and nonconcentrated urine samples

We evaluated a commercial enzyme immunoassay (EIA) kit for detection of Legionella pneumophila serogroup 1 soluble antigen by comparing it to radioimmunoassay (RIA), using both concentrated and nonconcentrated urine samples. The sensitivity of EIA was 67.4% in nonconcentrated urine samples and 82.6% in concentrated urine samples. The sensitivity of RIA was 60.9% and 84.8% in nonconcentrated and concentrated urine samples, respectively. Our study indicates that the sensitivity and specificity of EIA are comparable to those of RIA, and that concentrating the antigen by selective ultrafiltration increases sensitivity for both EIA and RIA, with no significant decrease in specificity.