Comparison of urine to sweat patch test results in court ordered testing.

A former cocaine and methamphetamine abuser was continuously monitored with both sweat patch and urine testing for approximately 6 months. Thirteen sweat patches were applied and collected, five were positive for cocaine and/or methamphetamine, but all the urine specimens collected were negative at the analytical cut-off levels. The high incidence of false positive sweat patch tests in relation to the sensitivity, specificity, and efficiency of the sweat patch assay is discussed. Possible mechanisms, which can lead to false positive results, are presented. The results of our study raise further questions about the preferential use of the sweat patch in detecting new episodes of drug use in formerly chronic drug users.

Comparison of cytobrushes with swabs for recovery of endocervical cells and for Chlamydiazyme detection of Chlamydia trachomatis.

Endocervical swab and cytobrush specimens from 1,301 symptomatic women were microscopically analyzed for adequacy and tested using Chlamydiazyme (CZ) (Abbott Laboratories). When the swab specimen was collected first, blocking antibody-confirmed CZ-positive results were obtained from 48 (8.0%) of 599 patients, 42 (87.5%) from swabs and 46 (95.8%) from cytobrushes (not significant). When the swab specimen was collected second, confirmed CZ-positive results were obtained from 46 (6.6%) of 702 patients, 44 (95.6%) from swabs and 41 (89.1%) from cytobrushes (not significant). Cytobrushes offered no significant advantage over swabs for CZ detection of Chlamydia trachomatis.

Efficacy of an enzyme-linked immunosorbent assay for detection of urinary tract immunoglobulins for diagnosis of urinary tract infections.

Results of the Uristat test (Shield Diagnostics Ltd.), a novel enzyme-linked immunosorbent assay (ELISA) for detection of urine antibodies to seven common bacterial pathogens, were compared with results of urine culture, urinalysis, and clinical history to determine the usefulness of Uristat in the diagnosis of urinary tract infections (UTIs). Midstream, catheterized, and indwelling catheter urine specimens sent to the laboratory for culture were included in the study. Quantitative cultures were performed on both 5% sheep blood agar and eosin-methylene blue agar. Uristat ELISAs were performed according to the manufacturer's instructions. By using a Bacillus subtilis bioassay technique, antibacterial activity was detected in the urine of 236 (22.2%) of 1,061 patients. Probable, possible, or asymptomatic UTIs were diagnosed for 258 (24.3%) of the 1,061 patients. Of those infections, 219 (84.9%) were caused by bacterial species whose antibodies were detectable by Uristat. Uristat's sensitivity and specificity were 76.7 and 56.0%, respectively. Uristat's predictive values of positive and negative results were 31.2 and 90.2%, respectively. Further development of the Uristat test is necessary before it can be of assistance in the diagnosis of UTIs.

Impact of endocervical specimen quality on apparent prevalence of Chlamydia trachomatis infections diagnosed using an enzyme-linked immunosorbent assay method.

Duplicate endocervical swabs were collected from 1824 patients for detection of Chlamydia trachomatis. Specimen pairs were combined into 400 microL of 0.9% saline solution. After vortexing, a 40-microL sample was smeared and stained with Papanicolaou's method for detection of endocervical and/or metaplastic (E-M) cells. The remaining specimen was tested for C trachomatis antigen with the use of an enzyme-linked immunosorbent assay (ELISA) procedure (Chlamydiazyme, Abbott Laboratories, North Chicago, Ill). Chlamydia trachomatis antigen was detected and confirmed (with the use of a blocking antibody [Abbott Laboratories]) in only 16 (1.7%) of 918 specimens that lacked detectable E-M cells, but it was detected significantly more frequently not only in 88 (13.3%) of 661 specimens that contained detectable E-M cells but also in 32 (13.1%) of 245 specimens that contained too many red blood cells to analyze microscopically. Of the initially positive ELISA results, none of 37 were falsely positive from specimens that contained 11 or more E-M cells, but significantly more (six [27.3%] of 22) were falsely positive from specimens that lacked detectable E-M cells. Variations in specimen quality had a significant impact on the incidence of both true-positive and false-positive ELISA results and could significantly influence understanding of the prevalence of chlamydial infections in women.

Detection of group A streptococci by aerobic culture and a new simplified immunoassay in three pediatric practices and a hospital laboratory.

Duplicate throat swabs for detection of group A streptococci were collected in three pediatric offices from 1,035 patients with symptoms of pharyngitis. In the collecting office and in the hospital laboratory, one swab from each patient was first inoculated to sheep blood agar (incubated at 35 degrees C aerobically for 2 days) and then tested for group A streptococcal antigen by using the SMART enzyme immunoassay technique (New Horizons Diagnostics Corp) incubated for up to 24 hours. Group A streptococci were recovered in culture (from one or both swabs) and serologically identified from 444 (42.9%) of the patients. Pediatric offices numbers 1, 2, and 3 detected 84.4%, 84.6%, and 82.2%, respectively, of their patients who had positive cultures (in the office and/or laboratory) by using their own culture system and 82.6%, 71.1%, and 84.9%, respectively, of these same patients by using the SMART technique. In the laboratory, SMART test sensitivity and specificity were 71.4% and 98.7%, respectively, after 5 minutes of test incubation. However, SMART test sensitivity improved to 86.5% after overnight incubation of the immunoassay and to 91.3% if the data from one defective lot of seven SMART production lots studied were excluded. SMART test results which are negative after 5 minutes of incubation should therefore be confirmed both by reincubation of the antigen test up to 24 hours and by culture.

Effect of endocervical specimen quality on detection of Chlamydia trachomatis and on the incidence of false-positive results with the Chlamydiazyme method.

Duplicate endocervical swabs were collected from 1,675 patients to assess the effects of variations in specimen quality on Chlamydiazyme (Abbott Laboratories) detection of Chlamydia trachomatis and the incidence of false-positive results. One swab (at random) from each patient was tested for C. trachomatis antigen by using the standard Chlamydiazyme procedure. A 200-microliter volume of 0.9% saline was added to the other swab from each patient. After vortexing, 20 microliters was smeared on a slide for Papanicolaou (Pap) staining and the remaining specimen was then tested with the Chlamydiazyme assay. The Chlamydiazyme result was positive for 170 (10.1%) and 165 (9.8%) of the stained and unstained duplicate specimens, respectively (no significant difference). Pap stains on smears from 1,536 (91.7%) of the patients were analyzed, and endocervical and/or metaplastic (E-M) cells were detected in 789 (51.4%) smears. Of these 1,536 stained and analyzed specimens, 150 (9.8%) were Chlamydiazyme positive but only 132 (88.0%) of the positive results were confirmed by repeating the test and using a monoclonal blocking antibody (Abbott). Confirmed Chlamydiazyme-positive results were obtained from only 34 (4.6%) of 747 specimens lacking E-M cells but from 98 (12.4%) of 789 specimens containing the cells (P less than 0.001). Of the 150 initially Chlamydiazyme-positive results obtained with Pap-stained, analyzed specimens, 12 (26.1%) of 46 were falsely positive from specimens lacking E-M cells but only 6 (5.8%) of 104 were falsely positive from specimens containing E-M cells (P less than 0.01). C. trachomatis antigen was detected significantly more frequently and false-positive results were significantly less common from specimens in which E-M cells were detected.

Effect of the pretest probability of intrauterine growth retardation on the predictiveness of sonographic estimated fetal weight in detecting IUGR: a clinical application of Bayes' theorem.

Four hundred and five women with singleton pregnancies and fetal age determination by crown-rump length were classified on the basis of their prenatal clinical findings into four risk categories for intrauterine growth retardation (IUGR), defined as a neonatal weight below the 10th percentile of age-dependent birth weight distribution curve. The incidence of IUGR in these four groups were 3.5% (very low risk), 20.6% (low risk), 49.6% (intermediate risk), and 88.0% (high risk). Severe growth retardation (birth weight less than 2.5th percentile) increased from 0% to 76.0% as the incidence of IUGR increased throughout the risk groups. The effect of these pretest risks on the prediction of severe IUGR by sonographic estimated fetal weight (EFW) was evaluated. The positive predictive value of the test, as well as the probability of having a growth-retarded infant after a normal EFW was obtained were considerably higher when the pretest probability of IUGR increased. In the very low risk group, the probability of severe IUGR was negligible regardless of the EFW. When the EFW was less than 10th percentile of our age-dependent EFW curve, the probability of severe IUGR in the other risk groups was high enough to warrant fetal well-being surveillance and/or timely interruption of gestation as appropriate. However, when the pretest probability was high, the risk of severe IUGR in spite of an EFW within the 10th percentile to 90th percentile remained sufficient to require fetal well-being surveillance as well. The study shows that placing ultrasound results in the context of the pretest risk of IUGR may improve clinical decision making in pregnancies complicated by fetal growth retardation.

Evaluation of fetal growth by ultrasonography in twin pregnancy: a comparison between individual and cross-sectional growth curve standards.

Cross sectional curves and individual fetal growth curves standards from the Rossavik growth model [P = c(t)(k + s(t]] were generated for abdominal and head circumferences, femur diaphysis length and estimated fetal weight from a sample of 59 women with twin pregnancy. These curves were compared to their counterparts in singleton pregnancies. Cross sectional curves of the four fetal anatomic parameters under study fell progressively below the curves for singletons during the last trimester of gestation. In contrast, there were few differences between individual fetal groWth curve standards for twin and singleton pregnancies. In 11 of the 59 patients, both methods were used to evaluate fetal growth in the last trimester of gestation. In 5 of these patients, fetal growth was normal by both methods in all 10 fetuses. In the 6 other patients, there were 3 fetuses with abormal estimated fetal weights (EFWs) by both population and individual standards. However, 3 fetuses had abnormal EFW's by populations standards but not by individual standards while the EFW of another fetus was abnormal by individual standards but not by population standards. These results illustrate that the cross-sectional approach to the assessment of growth in twins can be misleading and may lead to incorrect conclusions concerning the growth of these fetuses.

Efficacy of duplicate genital specimens and repeated testing for confirming positive results for chlamydiazyme detection of Chlamydia trachomatis antigen.

In an attempt to increase Chlamydiazyme (Abbott Laboratories) detection of Chlamydia trachomatis antigen and to establish the reproducibility of positive results, we carried out an investigation into the usefulness of testing duplicate specimens, of more aggressive endocervical specimen collection by using cytobrushes instead of swabs, and of the repeated testing of both specimens from patients with one or two positive results. Duplicate endocervical (female) and urethral (male) specimens, including one swab and one cytobrush specimen from 1,331 nonpregnant women, were collected from symptomatic and asymptomatic patients. Specimens were transported and tested for C. trachomatis antigen as specified by the manufacturer. Tests on all specimens from patients with positive results were repeated. Antigen was initially detected in one or both specimens from 210 (10.7%) of 1,968 patients, and repetition of the tests confirmed its presence in 198 (10.1%) of the patients, including all 183 patients in whom it was initially detected in both specimens. Initial results from at least 8 of the 12 patients with irreproducible antigen detection were most probably falsely positive. Results from 21 (10.6%) of the 198 patients for whom antigen detection was confirmed were repeatedly positive on only one specimen (9 [4.5%] on the second of the two specimens collected). Of 115 women from whom one swab and one cytobrush sample were taken and who had repeatedly positive results, antigen was detected in 7 (6.1%) only on the swab sample and in 4 (3.5%) only on the cytobrush sample. Use of the cytobrush does not appear justified with the Chlamydiazyme assay, and collection of duplicate specimens provided only a modest increase in detection of C. trachomatis. However, repeated testing of specimens when results from only one of two specimens are positive appears to be of clinical value.

Influence of the interval between time points on individual fetal growth curve standards derived from Rossavik models and two ultrasound scans before 26 weeks, menstrual age.

We studied the influence of the interval between the two scans used before 26 weeks' menstrual age to generate individual fetal growth curve standards utilizing the Rossavik growth model: P = c(t) kappa + s(t) (model specification functions previously reported). Intervals of 3 weeks to 12 weeks were suitable for predicting the growth of the abdominal and head circumferences and femur diaphysis length in individual fetuses. However, large systematic and random errors were found with intervals less than 5 weeks for three-dimensional parameters such as the head and abdominal cubes and estimated fetal weight. In addition, the data suggest that the systematic errors for these latter parameters may increase with intervals of 10 weeks or more. Overall, optimal individual fetal growth curve standards were best generated from two scans before 26 weeks' menstrual age separated by 5 weeks to 9 weeks.

Prediction of normal fetal growth by the Rossavik growth model using two scans before 27 weeks, menstrual age.

Individual growth curve standards for five fetal anatomic parameters (head and abdominal circumferences, head and abdominal cubes, and femur diaphysis length) and estimated fetal weight were prospectively developed in 70 pregnant women who delivered infants with growth considered appropriate-for-menstrual age. For this purpose, we used the Rossavik growth model (P = c(t) kappa + s(t], model specification functions previously reported, and the data of two scans before 27.0 weeks of menstrual age, separated by an interval of at least 5 weeks. The anatomic parameters and estimated weights of these fetuses in the last 14 weeks of gestation were found to have values close to their projected standards. Whereas there was a significant, although small, systematic error of overprediction for most of the parameters and estimated fetal weight, deviations between observed and expected values were, with few exceptions, within the ranges established by Deter for normal growth. This study demonstrates that the Rossavik growth model could be used to predict normal fetal growth in a sample of patients different from those from which the model was developed.

Predictiveness of sonographic fetal weight estimation as a function of prior probability of intrauterine growth retardation.

We evaluated the predictiveness of sonographically estimated fetal weight as a function of the estimation of probability of having intrauterine growth retardation (IUGR) before obtaining an ultrasound scan (prior probability). The value of the estimated fetal weight resided more in its high specificity than in its sensitivity, hence in its ability to confirm that the fetus is normal. The predictiveness of the method was further enhanced when the fetal weight estimation was placed in the context of the prior probability of IUGR. In particular, the positive predictive value of the test as well as the likelihood of having a growth-retarded infant in spite of an estimated fetal weight within the normal range were considerably higher as the prior probability of IUGR increased. Since the obstetrician using all available evidence is likely to form a rather good estimate of the possibility of IUGR before ordering a scan, this improvement in the predictiveness of estimated fetal weight through a Bayesian approach can be advantageously applied to ultrasound analysis and can effectively support clinical decision making.

Comparison of the TestPack Strep A enzyme immunoassay system with anaerobically incubated cultures for detection of group A streptococci from oropharyngeal swabs.

To find a rapid and sensitive test for detection of Group A streptococci (GABS), the performance of the TestPack Strep A (TPSA; Abbott) was compared with culture with the use of rayon-tipped throat swabs from symptomatic patients six months to 90 years of age. Each swab was first inoculated to a 5% sheep blood agar plate and then tested for GABS antigen with the use of the TPSA and the manufacturer's instructions. Cultures were incubated anaerobically at 35 degrees C for 36-48 hours unless positive results were obtained after one night. GABS were identified with a fluorescent antibody method or a latex antibody test. From 1,616 throat swabs, 296 (18.3%) of the cultures contained GABS. The sensitivity and specificity of the TPSA were 73.3% and 94.8%, respectively, whereas the predictive values of positive and negative results were 75.9% and 94.1%, respectively. Results varied significantly, however, with different production lots of TPSA. The TPSA does not appear to provide a sensitive alternative to an anaerobic culture for detection of GABS.

Influence of fetal growth patterns on sonographic estimation of fetal weight.

Six published fetal weight estimating regression models proposed for clinical use were evaluated in 259 pregnant women who delivered within 72 h of an ultrasound evaluation performed with sector scanner. The patient sample included 89 (33.2%) fetal weights that were below the 10th or above the 90th percentile for menstrual age. The actual mean percent error (systematic error), standard deviation (random error), and the number of large errors of prediction for all equations were greatest in fetuses that were small- and large-for-gestational age. Whereas there were no significant differences between equations for the patient sample as a whole, equation AC,BPD (Shepard) had the smallest systematic error in intrauterine growth retarded, premature, and normal-term fetuses less than 4000 g. Conversely, the systematic error of the models that included femur length was smallest at the upper end of the weight scale and in macrosomic fetuses in general. In that regard, the accuracy of fetal weight prediction could be increased by selecting the appropriate model for the proper clinical indications. Although these findings can be explained by the limitations of the current regression models in estimating fetal soft tissue mass, a subtle effect of the use of the sector scanner on the results of this study cannot be completely excluded and requires further investigation.

The prediction of fetal lung maturity by amniotic fluid fluorescence polarization in diabetic pregnancy.

Amniotic fluid fluorescence polarization was determined in 105 pregnant diabetic women who delivered between 31 and 41 weeks gestation within 48 hours of an amniocentesis. Seventy-seven of these 105 women had lecithin/sphingomyelin (L/S) ratio and phosphatidylglycerol (PG) determinations. Seven (6.6%) of the 105 neonates suffered from hyaline membrane disease (HMD). Fluorescence polarization at any cutoff value between 0.310 and 0.330 excluded reasonably well the possibility of HMD (false mature prediction rate, 2.7-3.4%). At these cutoff values, there was no difference in sensitivity and false mature prediction rate between fluorescence polarization and L/S ratio. However, PG determination was the most sensitive method and carried no false mature predictions.

Suitability of a throat culture method for evaluation of group A streptococcal antigen detection kits.

Previous reports have indicated a wide variation in observed sensitivity of antigen-detection kits for group A streptococci. Before undertaking an evaluation of these new kits, the sensitivity of the throat culture technic routinely used by this laboratory was reexamined. Each throat swab was directly inoculated to sheep blood agar containing trimethoprim-sulfamethoxazole (SXT X BA) and drug-free sheep blood agar (SBA) plates. Swabs were then washed in saline and the saline used to inoculate one more of each type of medium. SXT X BA cultures were incubated aerobically (5 to 10% CO2), and SBA cultures were incubated anaerobically, both for two days at 35 degrees C. From 726 patients, 164 (22.6%) of the specimens contained group A streptococci, 99% detected on directly inoculated cultures and 100% on cultures inoculated with the saline wash. Either an aerobically (CO2) incubated SXT X BA or an anaerobically incubated SBA, directly inoculated and held for two days, appears to offer a satisfactory reference culture method for the recovery of group A streptococci.

Distribution of bacteria and yeasts within the 10-ml Isolator during the processing of seeded blood samples.

Forty-five organisms consisting of stock cultures and clinical isolates of bacteria and yeast were separately inoculated into outdated blood bank blood to achieve a concentration of approximately 100 CFU/ml. Blood with each organism was introduced into groups of four Isolators (E. I. du Pont de Nemours & Co., Inc., Wilmington, Del.), which were then processed according to the Isostat instructions of the manufacturer. The supernatant, sediment, and wash (material removed from the surface of the slanted stopper after sediment removal) were inoculated onto 5% sheep blood agar plates. Cultures were incubated aerobically (5 to 10% CO2) at 35 degrees C for 48 to 72 h. From the 180 Isolators, the mean recovery was 6% (range, 0 to 48%) for the supernatant, 87% (range, 47 to 98%) for the sediment, and 8% (range, 3 to 23%) for the wash. Neither variation among technologists nor intentional misalignment of additional Isolators in the centrifuge could explain all of the losses of microorganisms from the sediment. The manual nature of the Isolator procedure, which led to the loss of significant amounts of organisms from the sediment, may help to explain false-negative Isolator results obtained from blood of patients, particularly when small numbers of pathogens are present.

Influence of gestational age on prediction of fetal lung maturity by fluorescence polarization of amniotic fluid.

Compared are the amniotic fluid fluorescence polarization values and the neonatal outcomes of 201 pregnant women who delivered from 28 through 37 weeks of gestation within 48 hours of the fluorescence polarization determinations. Thirty-five neonates developed hyaline membrane disease. The corresponding fluorescence polarization values ranged from 0.275 to 0.391. Eight of those 35 tests results were less than 0.325. The predictiveness of the method was studied using different threshold fluorescence polarization values. At the authors' own threshold of less than or equal to 0.325, the overall predictive value was as follows: false mature predictions: 6.2%, false immature predictions: 62.5%, sensitivity: 77.1%, and specificity: 72.8%. However, the false mature prediction rate was 21 to 40% from week 28 through week 33 versus 3.4 to 5.8% from week 34 through week 37, depending on the selected cutoff fluorescence polarization value. The sensitivity and specificity before, at, or after week 34 were significantly different at all tested fluorescence polarization values (P less than .05 to P less than .01) with the exception of the sensitivity at 0.310 and at 0.316 (P = .057). Caution is advised against relying on the fluorescence polarization method to predict fetal lung maturity at least before 34 weeks of gestation.

Evaluation of the dating of gestation via the growth adjusted sonographic age method.

We compared the actual delivery dates of 248 normal pregnant women to the estimated dates of confinement (EDC) calculated from one biparietal diameter measurement (BPD) between 18 and 26 weeks of gestation and to the EDCs corrected by the growth adjusted sonographic age ( GASA ) method. The dating of gestation by those two ultrasound methods also was compared to the calculation of the gestational age from the last menstrual period in a subgroup of 61 women with highly reliable clinical data. The GASA method had no advantage over the dating of gestation using one single BPD measurement obtained before 26 weeks, nor over the dating of gestation using reliable menstrual data.