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At the outset a distinction was made between criticisms directed at the validity of tests and criticisms not affected by the validity of the tests. It was noted further that all criticisms of tests must take into consideration the type of test and the use to which the test is put. Criticisms of the validity of tests involved the following issues: (i) tests may be unfair to certain groups and individuals, including the extremely gifted, the culturally disadvantaged, and those who lack experience in taking tests; (ii) tests are not perfect predictors of subsequent performance; (iii) tests may be used in overly rigid ways; (iv) tests may not measure inherent qualities of individuals; and (v) tests may contribute to their own predictive validity by serving as self-fulfilling prophecies. Criticisms that are more or less independent of test validity included the effects of tests on (i) thinking patterns of those tested frequently; (ii) school curricula; (iii) self-image, motivation, and aspirations; (iv) groups using tests as a criterion for selection or allocation, or both; and (v) privacy. Several concluding remarks are in order: 1) This paper has focused almost entirely on criticisms of tests. However, the positive value of standardized tests should not be ignored. Here we must keep in mind what possible alternative measures would be used if standardized tests were abandoned. 2) We must begin thinking about tests in a much broader perspective- one that includes consideration of the social effects of tests as well as their validity and reliability. 3) Finally, an effort should be made to develop rational and systematic policies on the use of tests with the culturally disadvantaged, the dissemination of test results, and the problem of invasion of privacy. Such policies can be formulated only if we are willing to take a long hard look at the role we want testing to play in the society. Standardized tests currently are a cornerstone in the edifice of stratification in American society. It is up to the social scientist to conduct research that will enable policy makers in education, business and industry, and government to determine in a consistent and rational way the ultimate shape of this edifice.
The Antibody Binding Test, a new technique for the evaluation of inactivated Rabies vaccines, developed by Arko, Wiktor and Sikes, was compared with the NIH- and Habel Test. Various vaccines were tested with these methods with the following results and conclusions. 1. The Habel Test was useful for testing of Hempt vaccines. With highly potent vaccines however it was not possible to get exact protection values, for all vaccinated mice were protected against all virus dilutions. 2. The NIH Test seemed to have an advantage over the Habel Test, since animals are vaccinated only twice, instead of 6 times, within two weeks. But this test was less suitable for the evaluation of Hempt vaccines. The requested Antigenic Value was reached only rarely with these vaccines. Repeated, NIH Tests gave widely differing results with Hempt vaccines. Vaccines which passed the NIH Test also passed the Habel Test, but not always vice versa. Antigenic Values of highly potent vaccines could be determined exactly with the NIH Test. This method is much better standardized by using a Standard vaccine in the test. The NIH Test is preferable for inactivated Rabies vaccines, with the exception of vaccines containing brain tissue, like the Hempt vaccine. 3. The Antibody Binding Test is a useful technique for the examination of inactivated cell culture vaccines. Consistent results can be achieved by skilled and experienced laboratory personnel. To avoid irregularities in the mortality rates, at least 10 mice should be used for each dilution of vaccine. With this method only Rabies virus antigen is measured which is bound by serum antibody during an incubation period of 60 min. Other factors supporting immunization like adjuvant- or booster-effects are not evaluated. Compared with the Habel and NIH Test the Antibody Binding Test is the best method for the evaluation of the amount of antigen in a Rabies vaccine. Hempt vaccines reached - as they did in the NIH Test - only Antigenic Values in this test. Vaccines with an Antigenic Value of larger than or equal to 0,3 in the Antibody Binding Test gave positive results also in the Habel and NIH Test, Vaccines with a Protection Value of 10-3 in the Habel Test and an Antigenic Value of 0,3 in the NIH Test did not always reach an Antigenic Value of 0.3 in the Antibody Binding Test.
BACKGROUND: Diagnosis of H. pylori infection may be made by endoscopic (invasive) tests, or by nonendoscopic (noninvasive) tests. Our aim was to evaluate recently available nonendoscopic tests, including two office-based serologic tests and a commercially available 13C urea breath test. METHODS: Gastric biopsy specimens (for culture and stain) from 178 patients (mean age 46 +/- 13.3 years, 79 men and 99 women), none of whom had received anti-H. pylori therapy, were tested for H. pylori infection. These tests were compared against two commercial serum IgG antibody immunoassays (Biowhittaker's Pyloristat, and Quidel), 2 office-based serum qualitative IgG antibody tests (FlexSure HP, and QuickVue One-Step), the Meretek 13C urea breath test, and the CLOtest (a biopsy urease test). RESULTS: The breath test (n = 147) had the best accuracy (96%) of the noninvasive tests studied. The serologic tests had similar accuracy to one another (84%-90%). The major drawback of the serologic tests was suboptimal specificity (75%-87%). Diagnosis of H. pylori based on the two office-based tests were not significantly different compared to the quantitative IgG antibody tests. The CLOtest had an accuracy of 97%. CONCLUSIONS: The Meretek 13C urea breath test is an excellent test, but is considerably more expensive than serologic tests. The FlexSure HP and the QuickVue One-Step office-based qualitative IgG serologic antibody tests gave similar results to laboratory based quantitative antibody tests, and are acceptable for initial diagnosis of H. pylori infection. The advantages of the office-based tests are low cost, simplicity, and immediacy of results.
The Advisory Committee on Existing Chemicals (BUA) of the Federal Republic of Germany convened a panel with expertise in reproductive and developmental toxicology to evaluate the OECD Screening Tests 421 (Reproduction/Developmental Toxicity Screening Test) and 422 (Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test) with respect to their ability to unmask any potential toxic effects on reproduction. The original assignment for that panel was to "validate" those screening tests. However, the panel members recognized beforehand that this was actually an impossible task because of lack of a sufficient database. Only five chemicals with known reproductive toxicity had been examined following the OECD Screening Test Guidelines 421 or 422. A comparison of these test results with those of the definitive OECD Test Guidelines 414, 415, 416, or additional investigations could, therefore, only have been made with this very limited number of chemicals that had also undergone evaluation by one of the test guidelines cited. In each case biological properties relevant to reproductive toxicity were also indicated by the OECD Screening Tests 421 or 422. This communication reviews the main differences in study design of OECD Screening Test Guidelines 421 and 422 compared to those definitive test guidelines of similar study design for reproduction or developmental toxicity (especially with the one-generation study, OECD Test Guideline 415). The very limited possibilities of detecting late postnatal and postlactational manifestations are emphasized, as is the low statistical power of the OECD Screening Tests 421 and 422. Furthermore, the very limited ability to unmask teratogenicity is delineated. The outcome of screening tests was evaluated based on the results of 57 studies conducted according to the OECD Test Guideline 421 or 422. The test results were categorized according to the incidence of toxic effects on reproduction in the parent animals or their offspring and related to general toxic effects. Based on the ranking of these results, recommendations regarding setting rational priorities for further evaluations of existing chemicals' reproductive hazards are made. In general, the reviewer panel supports the OECD position that the screening tests are useful for initial hazard assessment and can contribute to the decision-making process on setting priorities for further test requirements. The panel also agrees with the OECD statement that the OECD Screening Tests 421 and 422 are neither an alternative to definitive tests (i.e., OECD Test Guidelines 414, 415, and 416) nor are they intended as their replacement.
The Rappaport rapid (RR) plate and card tests were developed as modifications of the RR tube test to permit rapid and inexpensive screening of large numbers of subjects for the diagnosis of syphilis. More than 2,000 sera were examined in parallel by the Venereal Disease Research Laboratory (VDRL) slide test, the rapid plasma reagin (RPR) card test and the RR plate and card tests. There was complete agreement between the RR plate and card tests and the VDRL slide and RPR card tests in 96.6% of sera. In a selected group of 1,530 sera examined, in addition, by the fluorescent treponemal antibody absorption (FTA-ABS) test, there was agreement between the RR plate and card tests and the FTA-ABS test in 74.3% of sera and between the VDRL and RPR tests and the FTA-ABS test in 73.7% of sera. The RR plate test was found to be sufficiently sensitive and specific for the diagnosis of syphilis, although the VDRL slide test is perhaps more sensitive in primary and late latent syphilis. Since the antigen used in the RR tests is colored and stable and the sera do not require inactivation before the test, the tests are easier to perform than the VDRL slide test: the RR plate and card tests could therefore replace the VDRL test as a screening test, with hardly any loss of accuracy.
A comparative study has been performed on test methods for assessing the biodegradability of chemicals in seawater environments. A simple shake flask die-away test with natural seawater and 14C-labeled chemicals added in microgram/liter concentrations is proposed as a "simulation" test. The analytical parameter used in this test is residual dissolved 14C activity. The performance of the simulation test has been compared with the performance of similar screening tests with dissolved organic carbon analysis and test compounds added in mg/liter concentrations to nutrient-enriched seawater. All chemicals investigated that passed the screening tests were also degradable in the simulation test and some results with simulation tests were positive; even screening tests were negative, while some compounds, including maleinhydrazide, known to be degradable in soil, remained undegraded in either type of test. Disappearance times after the ended lag time were smaller in screening tests than in simulation tests, but the rates of biodegradation cannot be meaningfully compared, as zero-order kinetics in combination with an exponentially growing population of degraders prevail in screening tests, while first-order kinetics and frequently a constant activity of degraders (cooxidation) prevail in simulation tests where the test material is a secondary substrate only. In screening tests, lag times are sometimes excessively long and highly variable. Whether the lag times could be decreased and their variability narrowed by supplementation with a cosubstrate (yeast extract) or by inoculation with seawater that had been preadapted to the test material was investigated. In most experiments such test modifications had no significant effect but in one experiment with 4-nitrophenol, inoculation with 1% preadapted seawater decreased the lag phase from greater than 35 to 9 days.
The short ACTH stimulation test is an easy, reliable, and extensively used test in the assessment of the hypothalamo-pituitary-adrenal (HPA) axis. However, its use immediately after pituitary surgery is a matter of debate. The insulin tolerance test (ITT) is the gold standard in the evaluation of the HPA axis, but it is not always without side effects and may be unpleasant early after pituitary surgery. Our aim was to investigate the value of the 1-microg ACTH test in the assessment of the HPA axis early after pituitary surgery. We also aimed to determine the value of the 1-microg and 250-microg ACTH tests and the ITT in the estimation of HPA axis status after 3 months postoperatively. Nineteen patients subjected to pituitary tumor surgery were included in the study, and the ITT and the 1-microg and 250-microg ACTH tests were performed between the 4th and 11th days of surgery. The tests were repeated at the first month in 3 patients with subnormal peak cortisol responses (454, 125, and 301 nmol/L) and in 18 patients at the third month postoperatively. ACTH stimulation tests were performed by using 1 microg and 250 microg ACTH iv as a bolus injection, and blood samples were drawn at 0, 30, and 60 min for measurement of serum cortisol levels. The ITT was performed by using iv regular insulin, and serum glucose and cortisol levels were measured. The 1-microg and 250-microg ACTH stimulation tests and the ITT were performed consecutively. At least 48 h were allowed between each test. A peak serum cortisol level of 550 nmol/L or greater was considered as a normal response for both the ITT and the ACTH tests. The serum cortisol level was measured by RIA using commercial kits. Serum glucose was determined by glucose oxidase method. There were correlations between the peak cortisol response to the ITT and the 1-microg ACTH test (r = 0.39, P < 0.05) in the early postoperative period. No correlation was found between the ITT and the 250-microg ACTH test responses. In the early postoperative period, two patients showed normal cortisol responses (> or =550 nmol/L) to the 1-microg ACTH test and five patients showed normal cortisol responses to the 250-microg ACTH test among the six patients with subnormal cortisol responses to the ITT. Three patients with subnormal cortisol responses to ITT and baseline cortisol values less than 240 nmol/L showed normal HPA axis at the end of the first month. In the late postoperative period, at the third month, all the patients showed normal HPA axis. In the early postoperative period of pituitary surgery, the 1-microg ACTH test results are more concordant than the 250-microg ACTH test in comparison with the ITT. Our results also indicate that HPA axis dysfunction shown by ACTH stimulation tests and the ITT in early postoperative period may be normalized 1-3 months after surgery. For this reason, we think that dynamic tests including the ITT may not be useful early after pituitary surgery.
BACKGROUND: There currently is debate on whether to include new assays for viral antigens and nucleic acids in the battery of screening tests applied to all blood donations. Proposals call for implementation of p24 antigen screening tests to help identify donors who are infected with human immunodeficiency virus type 1 (HIV-1) but have not yet seroconverted (window-period donors). There is concern, however, that people at higher risk for HIV infection will be attracted to blood centers in order to obtain the results of an HIV assay that is not routinely available elsewhere. Therefore, the benefit of antigen testing may be offset by an increase in the HIV incidence rate among blood donors. STUDY DESIGN AND METHODS: Estimates were obtained from previous reports for the HIV incidence rate among blood donors, the percentage of donations from test-seeking donors, the duration of the HIV-infectious window period, and the performance of p24 antigen screening assays. Sensitivity analyses were performed by using various percentages of test-seeking donors following implementation of antigen testing and various HIV incidence rate ratios of test-seekers to nonseekers. Hypothetical residual HIV risks were calculated for multiple scenarios and compared to the current estimate of HIV risk without antigen screening of blood donations. RESULTS: If antigen testing reduces the window period by 27 percent (e.g., from 22 days to 16 days), and the HIV incidence rate among test-seekers is 30 times that among nonseekers, then the benefit of antigen testing will be eliminated if the percentage of test-seekers (currently estimated at 3.2%) increases to 5.7 percent. If antigen testing reduces the window period by approximately 45 percent (e.g., from 22 days to 10 days or from 13 days to 6 days) and the HIV incidence rate ratio (test-seekers vs. nonseekers) is assumed to be equal to the HIV prevalence ratio (5.3), then the percentage of donations from test-seeking donors would have to increase to 25 percent of all donations to offset the benefit of antigen screening. CONCLUSION: This model helps identify the key measures for assessing the potential adverse effect of increased test seeking as a consequence of the addition of p24 antigen (or other direct virus) assays to blood donor screening programs. In most scenarios, the beneficial effect of antigen screening exceeded the potential detrimental effect of attracting higher-risk, test-seeking donors. The possibility cannot be ruled out, however, that a subgroup of high-risk, test-seeking donors attracted to the blood centers by a new HIV test will offset the reduction in the residual risk of HIV infection associated with antigen screening.
The rapid plasma reagin (RPR) card test manufactured by Beckman Instruments, Inc., was compared, qualitatively and quantitatively, with the Venereal Disease Research Laboratory (VDRL) slide test and the standard RPR 18-mm circle card tests for the serodiagnosis of syphilis. Sera from 638 individuals were used in this study. Two pilot lots and two production lots of antigen were submitted by Beckman Instruments, Inc., for evaluation. Qualitative agreement among the three RPR card tests was 98.1%; between the Beckman RPR card and the VDRL slide tests, 95.0%; and between the reference RPR card and the VDRL slide tests, 95.5%. The Beckman RPR card test was 95.3% specific, whereas the specificities of the reference RPR card and the VDRL slide tests were 98.8% and 96.1%, respectively. Sensitivities of the three nontreponemal tests were: Beckman RPR card test production lots, 94.7%; reference RPR card test, 96.8%; and VDRL slide test, 90.6%. Quantitative agreement +/- 1 dilution among the three RPR card tests was 93.0%, whereas quantitative agreement was approximately 40% when both RPR card tests were compared with the VDRL slide test. We found the Beckman RPR card test comparable to the standard RPR card tests. Therefore, the decision of which test to use for the serodiagnosis of syphilis is at the discretion of the user.
Under the Clinical Laboratory Improvement Amendments of 1988 (CLIA), simple, low-risk tests can be waived and performed with no routine regulatory oversight in physicians' offices and various other locations. Since CLIA was implemented, waived testing has steadily increased in the United States. Surveys conducted during 1999-2004 by the Centers for Medicare & Medicaid Services and studies funded by CDC during 1999-2003 evaluated testing practices in sites holding a CLIA Certificate of Waiver (CW). Although study findings indicate CW sites generally take measures to perform testing correctly, they raise quality concerns about practices that could lead to errors in testing and poor patient outcomes. These issues are probably caused, in part, by high personnel turnover rates, lack of understanding about good laboratory practices, and inadequate training. This report summarizes study findings and provides recommendations developed by the Clinical Laboratory Improvement Advisory Committee for conducting quality waived testing. These recommendations include considerations before introducing waived testing, such as management responsibility for testing, regulatory requirements, safety, physical and environmental requirements, benefits and costs, staffing, and documentation. They also cover good laboratory practices for the three phases of testing: 1) before testing (test ordering and specimen collection), 2) during testing (control testing, test performance, and result interpretation and recording), and 3) after testing (result reporting, documentation, confirmatory testing, and biohazard waste disposal). They are intended to be used by those who would benefit from improving their knowledge of good laboratory practices. Continued monitoring of waived testing, with a focus on personnel education and training, is needed to improve practices and enhance patient safety as waived testing continues to increase.
Although tests for detection of immunoglobulin M (IgM) toxoplasma antibodies have been reported to have a high degree of accuracy, it is well recognized by investigators in the United States and Europe that false-positive results may occur with many of these tests, at times to an alarming degree. Unfortunately, this information is not well documented in the literature. Studies on various toxoplasma IgM test kits are frequently flawed. The investigators often use reference tests which have not previously been carefully evaluated as well as sera that were not appropriate to answer the question of how often false-positive results might occur. We recently had the unique opportunity to evaluate the accuracy of the Platelia Toxo IgM test in 575 serum samples obtained during an outbreak of toxoplasmosis which occurred in 1995 in the Capital Regional District of British Columbia, Canada. When compared with results obtained in a reference IgM enzyme-linked immunosorbent assay (ELISA), the Platelia Toxo IgM test had a sensitivity of 99.4%, specificity of 49.2%, positive predictive value of 51.9%, negative predictive value of 99.3%, and an overall agreement of 67.0%. In an attempt to resolve discrepancies between these two tests, a serological profile (Sabin-Feldman dye test, IgA and IgE antibody tests, differential agglutination [AC/HS] test, and IgG avidity method) was performed. Of 153 serum samples that were positive in the Platelia Toxo IgM test and negative in the IgM ELISA, 71 (46.4%) were negative in the Sabin-Feldman dye test. Of the serum samples that were positive in the dye test, 77 (93.9%) had a serological profile most compatible with an infection acquired in the distant past. These results reveal high numbers of false-positive results in the Platelia Toxo IgM test and highlight the importance of appropriate evaluation of commercial tests that are currently being marked. Our results also emphasize the importance of confirmatory testing to determine whether the results of an IgM antibody test reflect the likelihood of a recently acquired infection.
OBJECTIVE: Heat exposure has been shown to stimulate GH release, but the specificity and the reproducibility have not been determined, and the test has not been compared with validated GH stimulation tests in adulthood. We therefore tested the specificity and the reproducibility of the heat exposure test in healthy subjects and compared the results with those obtained with the insulin-tolerance test (ITT). DESIGN: Ten healthy non-obese men, aged 31.3+/-4.80 years, underwent four GH stimulation tests in random order: two ITTs and two heat exposure tests. In the heat test, subjects were placed in a hot bath with water temperature at 40.3+/-0.11 degrees C for 45 min, resulting in an identical (P = 0.477) significant increase in tympanic temperature of 1.26+/-0.05 and 1.41+/-0.07 degrees C in the two tests. RESULTS: Peak GH response to the heat exposure test was less than the peak GH response to ITT (5.25+/-1.72 vs 15.5+/-3.17 microg/l, P = 0.006). Furthermore the specificity (arbitrary cut-off level = 3 microg/l) of the heat test was lower than of the ITT (8/17 vs 18/20, P = 0.006). The coefficient of variation did not differ between the two tests (heat test 0.31, ITT 0.36, P = 0.77). Peak GH values in the individual tests were highly correlated (heat, r = 0.908, P = 0.002; ITT, r = 0.815, P = 0.004). Reproducible increments in the circulating levels of stress hormones were observed during ITT. but these hormones remained largely unchanged during heat exposure. CONCLUSIONS: The heat exposure test is not a reliable GH stimulation test compared with the ITT in adults. This study documents that the ITT has a high specificity and reproducibility in the diagnosis of GH deficiency in adulthood. We propose that the heat exposure test is not used in the diagnosis of this condition in adulthood.
The relationships among race, face validity perceptions, test-taking motivation, and test performance on a cognitive ability test were examined. Undergraduates completed 2 parallel cognitive ability tests and a test reactions measure. Results showed that test-taking motivation was related positively to subsequent performance on a parallel test even after the effects of race and performance on the first test were controlled. The effect of race on subsequent test performance was found to be mediated partially by motivation that provided evidence that some portion of the Black-White difference in test performance may be explained through differences in test-taking motivation. Results also indicated that Black-White differences in face validity perceptions of the test may be a function of Black-White differences in test performance. Face validity perceptions of the test affected subsequent performance on the parallel test but only indirectly through test-taking motivation.
International test guidelines, such as the Organisation for Economic Cooperation and Development (OECD) guideline #406, recommend 2 guinea pig methods for testing of the contact allergenic potential of chemicals: the Guinea Pig Maximization Test (GPMT) and the Buehler test. Previous comparisons between the methods suggested that the Buehler test was less sensitive than the GPMT although modified Buehler test protocols were used. Parallel GPMT and Buehler tests were conducted according to OECD guideline #406 using a multiple-dose design and test results were analysed using a standard logistic dose-response model. To compare the sensitivity of the 2 test procedures the test conditions were kept identical and the following chemicals with a range of sensitization potentials were tested: chloraniline, chlorhexidine, eugenol, formaldehyde, mercaptobenzothiazole and neomycin sulphate. Formaldehyde and neomycin sulphate were strong sensitizers in both tests. Mercaptobenzothiazole, eugenol and chloraniline were all strong sensitizers in the GPMT, eugenol and mercaptobenzothiazole were negative in the Buehler test and equivocal results were obtained with chloraniline. Chlorhexidine was negative in the GPMT and equivocal responses were obtained with the Buehler test. Higher induction concentrations were needed to show allergenicity in the Buehler test and for some allergens the Buehler test protocol was not sensitive enough to demonstrate allergenic potential.
A comparative study of fluconazole and amphotericin B susceptibility testing was performed with 68 clinical Candida species isolates and three test methods. The methods used were an agar diffusion method (E-test) and two broth dilution methods, the National Committee for Clinical Laboratory Standards (NCCLS) reference broth macrodilution method and an in-house-prepared semiautomated broth microdilution method based on the Bioscreen turbidometer. In the microdilution method, growth of the yeasts was measured continuously by the automatic turbidometer (Bioscreen), which permitted precise and objective determination of endpoints. MIC endpoints were read after 24 h for the microdilution method and the E-test. Amphotericin B susceptibility testing with the NCCLS method and the E-test yielded comparable results in 89% of the tests, meaning that the endpoints obtained were identical or differed by no more than 2 twofold dilutions. The NCCLS and broth microdilution tests scored 97% comparable results, and the E-test and the broth microdilution test yielded 90% comparable results. Fluconazole susceptibility testing produced 96% comparable results with the NCCLS test and the E-test, 100% comparable results with the NCCLS and the microdilution methods, and 98.5% comparable results with the microdilution method and the E-test. We conclude that the E-test and the Bioscreen microdilution method are valuable alternatives to the NCCLS reference method for routine susceptibility testing of Candida species with fluconazole and amphotericin B.
The performance of eight methods in identifying Neisseria species, particularly N. gonorrhoeae, was evaluated. These methods included four rapid carbohydrate utilization tests (Gonobio-Test, Neisseria-Kwik, RIM-N, and Minitek); the Gonochek II, a test which is based on the utilization of chromogenic substrates; and three monoclonal antibody tests (Syva MicroTrak, GonoGen, and Phadebact Monoclonal GC OMNI Test). In all, 182 isolates comprised in six species of Neisseria as well as Branhamella catarrhalis and Moraxella sp. were tested. Cystine-tryptic digest agar supplemented with sugars was included for reference purposes. In the carbohydrate utilization tests, the sensitivity and specificity of the Neisseria-Kwik and Minitek tests for the identification of N. gonorrhoeae were 100%. This compared with sensitivities and specificities, respectively, of 100 and 99.1% for the Gonobio-Test and 99.1 and 100% for cystine-tryptic digest agar sugars and the RIM-N test. The sensitivity and specificity of the Gonochek II test were 99.0 and 86.7%, respectively. Although most test kits did not claim to identify all Neisseria species, in several cases isolates of N. subflava were misidentified or could be misinterpreted as N. gonorrhoeae or N. meningitidis. With the monoclonal reagents, the Syva MicroTrak system was 100% sensitive and 100% specific. The GonoGen test was both 99.1% sensitive and specific, while the Phadebact Monoclonal GC OMNI Test was 99.1% sensitive but 91.2% specific. With this latter test, cross-reactions were observed with strains of B. catarrhalis, N. cinerea, and N. lactamica.
BACKGROUND: This study evaluated the change from a rapid plasma reagin (RPR) test to an automated specific treponemal test (PK-TP) in screening for syphilis in blood donors. STUDY DESIGN AND METHODS: A cross-sectional seroprevalence analysis was performed on 4,878,215 allogeneic blood donations from 19 American Red Cross Blood Services regions from May 1993 through September 1995. Positive predictive values relative to the confirmatory fluorescent treponemal antibody absorption test (FTA-ABS) were calculated. Differences in seroprevalence were compared in RPR and PK-TP tests for 1) unconfirmed and confirmed tests, 2) first-time and repeat donors, and 3) "recent" versus "past" infections. Donation data from three additional Red Cross regions were evaluated for repeat donation patterns of blood donors who had a donation that was positive in a serologic screening test for syphilis. The value of RPR and PK-TP tests as surrogate markers for HIV infection was compared. RESULTS: Reactive rates were lower but the positive predictive values was higher for the PK-TP test than for the RPR test. Initially, donors screened by PK-TP were more likely to be confirmed as positive than were donors screened by RPR, but these rates became comparable. It is estimated that a single HIV window-period donation was removed by serologic testing for syphilis each year of this study period. CONCLUSIONS: The change to the PK-TP test resulted in a lower repeatedly reactive rate, better prediction that a confirmed-positive test for syphilis would occur in testing in the FTA-ABS, fewer donations lost, and comparable deferral rates. Because of the high rate of reactivity to serologic testing for syphilis among donors previously confirmed positive for syphilis, indefinite deferral after a confirmed-positive index donation may be warranted. Serologic testing for syphilis is ineffective as a marker of HIV-infectious window-period donations.