Detection of immunoglobulin M in cerebrospinal fluid from syphilis patients by enzyme-linked immunosorbent assay.

Cerebrospinal fluid (CSF) samples were evaluated in an immunoglobulin M enzyme-linked immunosorbent assay (IgM ELISA) for syphilis with sonic extracts of Treponema pallidum coated on polystyrene plates. The ELISA procedure was reproducible, and T. pallidum antigens were stable., A total of 15 CSF samples from patients with neurosyphilis, 18 CSF samples from patients with syphilis, 12 CSF samples from patients treated for syphilis, and 494 CSF samples from patients with neurologic or other systemic diseases were tested. The IgM ELISA gave reactive results in all of six symptomatic and congenital neurosyphilitic patients and none of nine asymptomatic neurosyphilitic patients. Of 524 CSF samples from nonneurosyphilitic individuals, 513 were nonreactive, resulting in 98% test specificity. The IgM ELISA in CSF should prove to be useful for confirmation of symptomatic neurosyphilis.

Staining intensities in the fluorescent treponemal antibody-absorption (FTA-Abs) test: association with the diagnosis of syphilis.

In 1984 the reporting system for the fluorescent treponemal antibody-absorption (FTA-Abs) test was changed by the Centers for Disease Control (CDC; Atlanta, GA) to eliminate the borderline report. Factors influencing the reliability of the FTA-Abs test results, i.e., sensitivity, specificity, prevalence of syphilis, prescreening of sera with nontreponemal tests, and reproducibility, were considered before the change in the reporting system was recommended and are reported here. The borderline report, when associated with syphilis, was most frequently also associated with the diagnosis of early primary, dark-field-positive, nontreponemal test-nonreactive syphilis. Whereas elimination of the borderline report decreased the sensitivity of the FTA-Abs test as a confirmatory test from 100% to 99.5%, the specificity increased from 82.5% to 88.7%. The 1+ staining intensity had an association of approximately 5% with the diagnosis of syphilis. The changes in the reporting system were designed to assist the clinician in interpreting the results of the FTA-Abs test in those cases that present diagnostic dilemmas.

Adenovirus ELISA for the evaluation of cerebrospinal fluid in patients with suspected neurosyphilis.

An enzyme-linked immunosorbent assay (ELISA) detecting antibodies against the adenovirus group antigen was used to examine cerebrospinal fluid (CSF) of suspected neurosyphilis patients for serum contamination or blood-brain barrier (BBB) leakage. Adenovirus antibodies are ubiquitous, produce high antibody titers, and rarely cause central nervous system (CNS) infections. Of 52 normal adult sera tested with this ELISA, only one lacked antibodies. CSF from 48 healthy individuals did not present a detectable amount of anti-adenovirus antibodies. CSF from 33 suspected neurosyphilis patients with positive results in the fluorescent treponemal antibody-absorption (FTA-ABS)-CSF test were examined. Eighteen showed anti-adenovirus antibodies indicating contamination of the CSF with peripheral blood or damaged BBB by syphilis or other disease, resulting in questionable CSF treponemal results. The remaining 15 of these patients appeared to be producing their anti-treponemal antibodies in the CNS. This procedure may prove to be of considerable help in excluding false positive FTA-ABS results in CSF samples.

Interlaboratory comparison of the toluidine red unheated serum test antigen preparation.

The toluidine red unheated serum test (TRUST) antigen, a macroscopic flocculation test antigen developed by Pettit et al. (J. Clin. Microbiol. 18:1141-1145, 1983) by modifying the color-coded antigen of Kasatiya and Lambert (Appl. Microbiol. 28:317-318, 1974), was compared with the Venereal Disease Research Laboratory (VDRL) slide and rapid plasma reagin (RPR) 18-mm circle card tests for sensitivity, specificity, and reproducibility. Two lots of TRUST antigen were prepared by two laboratories in the Centers for Disease Control. Both laboratories performed the TRUST and VDRL slide test on serum samples from 1,102 patients attending the DeKalb County, Georgia, Sexually Transmitted Disease Clinic. In addition, one laboratory performed the RPR card test. Reactive sera were quantitated in the three nontreponemal tests and confirmed with the fluorescent treponemal antibody absorption test. The sensitivity in untreated syphilis for all nontreponemal tests involved was 98.4%. The specificity for these tests was 98.6%. The qualitative reproducibility among the four lots of TRUST antigen, VDRL slide, and RPR card tests was 98.2%. Only 20 sera showed discrepant results. Intralaboratory reproducibility of the two TRUST antigens was 100% for one laboratory and 99.6% for the other. Interlaboratory reproducibility for the four lots of TRUST and the VDRL slide test was 99%. Quantitative agreement +/- 1 dilution between the TRUST and RPR card test was 92.3%, and quantitative agreement +/- 1 dilution for the TRUST and RPR card test versus the VDRL slide test averaged 50%. The TRUST appeared to be comparable to the RPR card test in all parameters compared.

Toluidine red unheated serum test, a nontreponemal test for syphilis.

We have shown that a modification of the color-coded antigen developed by Kasatiya and Lambert (Appl. Microbiol. 28:317-318, 1974) can be used as a substitute for other nontreponemal antigens used in screening tests for syphilis. The antigen is based on the Venereal Disease Research Laboratory antigen, with EDTA, choline chloride, and toluidine red toner added. Performance of the toluidine red unheated serum test (TRUST) is identical to that of the rapid plasma reagin 18-mm circle card test (U.S. Department of Health, Education, and Welfare, Public Health Service Publication no. 411). In a series of preliminary evaluations, the TRUST antigen was found to be stable over a period of 6 months at 4 degrees C. In a comparison of TRUST with the rapid plasma reagin card test, the qualitative agreement was 100%, whereas agreement between these two tests and the Venereal Disease Research Laboratory slide test was 99.7%. The quantitative agreement +/- 1 twofold dilution between TRUST and the rapid plasma reagin card test was 100%; between TRUST and the Venereal Disease Research Laboratory slide test it was 75.0%; and between the rapid plasma reagin card and Venereal Disease Research Laboratory slide tests it was 60.0%.

Comparison of a new rapid plasma reagin card test with the standard rapid plasma reagin 18-mm circle card test and the venereal disease research laboratory slide test for serodiagnosis of syphilis.

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.

EDTA-treated plasma in the rapid plasma reagin card test and the toluidine red unheated serum test for serodiagnosis of syphilis.

Both the rapid plasma reagin (RPR) 18-mm circle card test and the toluidine red unheated serum test (TRUST) were designed to be more rapid than the Venereal Disease Research Laboratory slide test for the serodiagnosis of syphilis. The RPR card test, although originally designed as the teardrop card test for use with plasma, has received recognition from the Centers for Disease Control as a standard test for syphilis for use with serum samples only. In this study, 132 EDTA plasma-serum pairs were tested in both the RPR card test and TRUST immediately after the blood was drawn and the serum or plasma was separated from the cellular constituents of the blood. The plasma samples were further tested at 24-h intervals of storage at 25 and 4 degrees C for 72 h. Special attention was paid to any increase in roughness in nonreactive specimens. The greatest increase in roughness (16.7%) was seen with the TRUST after 72 h at 25 degrees C. An additional 174 plasma-serum pairs were tested after 18 h of storage at 25 degrees C. Comparisons of the results of the 306 serum specimens with their corresponding plasma pairs gave 99.0% qualitative agreement for both tests. Quantitative agreement +/- 1 dilution between serum-plasma pairs tested within 18 h was 92.1% (35 of 38) for the RPR card test and 94.1% (32 of 34) for the TRUST. Our results with plasma from blood drawn with EDTA as the anticoagulant were comparable with results with serum specimens for both tests when plasma specimens were tested within 18 to 24 h.

Evaluation of a new rapid plasma reagin card test as a screening test for syphilis.

This study evaluates the American Dade (Biokit Laboratories) rapid plasma reagin (Dade RPR) card test, currently used in Spain for the diagnosis of syphilis, which has been recently released to the U.S. market. Used as a basis for comparison with the Dade card test were the 18-mm standard rapid plasma reagin (standard RPR) card test and the Venereal Disease Research Laboratory (VDRL) slide test, using both fresh sera obtained from 505 individuals and paired serum-plasma specimens from 174 individuals. Results obtained proved the Dade RPR card test with serum to be very similar to the standard RPR card test; sensitivity was 92.3% and specificity was approximately 99% for both RPR card tests. Although the sensitivity of the VDRL slide test was lower at 88.5%, its specificity was also approximately 99%. Quantitatively, the agreement +/- 1 dilution between the two card tests was 93.6%. Agreement +/- 1 dilution between the Dade RPR card test and the VDRL slide test was 46.5% for sera, comparable to the standard RPR-VDRL agreement of 50%. In the limited evaluation of the RPR card tests with plasma, the specificity was 99.4% and the sensitivity was 100% for both tests. Quantitative agreement +/- 1 dilution between plasma and serum pairs was 100% for the Dade RPR card test. Our results showed that the Dade RPR card test is as sensitive and as specific as the standard RPR card test. Therefore, it was concluded that one card test has no particular advantage over the other.

Heated versus unheated sera in the hemagglutination treponemal test for syphilis.

Sera (920) were tested to evaluate the use of heated versus unheated sera in the hemagglutination treponemal test for syphilis. The heated and unheated samples were tested on the same day with the hemagglutination treponemal test for syphilis kit according to the manufacturer's protocol. Agreement of results between the heated and unheated sera was 99.2%. The reading pattern of agglutination was clearer and more distinct with heated sera; therefore, based solely on our preference for the reading patterns, we suggest that heated sera be used in the hemagglutination treponemal test for syphilis.

Specificity, sensitivity, and reproducibility among the fluorescent treponemal antibody-absorption test, the microhemagglutination assay for Treponema pallidum antibodies, and the hemagglutination treponemal test for syphilis.

Using 920 sera, we compared the specificity and reproducibility of the hemagglutination treponemal test for syphilis with those of the fluorescent treponemal antibody-absorption test and the microhemagglutination assay for Treponema pallidum antibodies; we found all three tests to be comparable. However, the hemagglutination treponemal test for syphilis, like the microhemagglutination assay for T. pallidum antibodies, lacked sensitivity in sera from patients with primary syphilis.

Vi serology in the detection of typhoid carriers.

A new haemagglutination assay for Vi antibodies was evaluated in searches for symptom-free carriers of Salmonella typhi associated with sporadic cases of typhoid fever. The assay differs from previous ones in that a purified (instead of crude) Vi antigen from Citrobacter was used to sensitise the red blood cells. In ten sporadic outbreaks of typhoid stool culture identified seven enteric carriers of S. typhi among the patients' families or other close contacts. All seven carriers had Vi antibodies in titres ranging from 1:40 to 1:2560. Moreover, among thirty-seven stool-culture-negative contacts of patients, only one had Vi antibodies, in a titre of 1:10. Thus, the new assay for Vi antibodies was as sensitive and as specific as faecal culture in detecting symptom-free typhoid carriers. It could become a convenient screening test.

Evaluation of a new assay for Vi antibody in chronic carriers of Salmonella typhi.

The assay for serum antibody to the Salmonella typhi capsular polysaccharide (Vi) antigen has recently been revised because of the availability of a purified, highly polymerized Vi antigen. We compared this revised Vi antibody assay to the traditional one for potential usefulness in the surveillance of chronic enteric carriers of S. typhi. The purified Vi antigen of Citrobacter freundii was incorporated into a passive hemagglutination assay for serum Vi antibody; the standard Vi antibody assay was also a hemagglutination assay that employed as the Vi antigen a crude extract of Citrobacter (Ballerup O group 29). As determined by the revised assay, Vi antibody was found in the sera of 22 (71%) of 31 current typhoid carriers, none of 6 resolved carriers, and none of 22 control subjects. According to the traditional assay, Vi antibody was present in 23 of those current carriers (74%), 1 of the resolved carriers (17%), and 4 of the control subjects (18%). The rate of false-positive Vi antibody tests among resolved carriers and control subjects was less with the revised assay (P < 0.05). Successful antimicrobial therapy resulted in a reversion to seronegativity within 1 year in 8 of 10 Vipositive carriers according to the revised assay, but in only 3 of 11 according to the standard assay (P < 0.05). During a 2-year period of observation, 15 (94%) of 16 current typhoid carriers had at least one positive purified Vi antibody test; among 12 of those patients with Vi titers of 1:40 or greater, 9 (75%) were continuously Vi positive. Thus, the revised Vi antibody assay is more specific and no less sensitive than the standard assay for the condition of current enteric carriage of S. typhi. This serological test could be of value in the surveillance of typhoid carriers by public health agencies.

Use of stable, sensitized cells in an indirect microhemagglutination test for melioidosis.

Two evaluations were carried out in this study. The first was a comparison of the standard tube test with the automated microtitration test for the detection of antibodies to Pseudomonas pseudomallei by the indirect hemagglutination method. Data from this comparison indicated that the tests were equivalent. The second evaluation consisted of reproducibility studies on two lots of pyruvic aldehyde-stabilized sensitized erythrocytes in comparison with freshly prepared sensitized erythrocytes in the automated microtitration test. The influence of different types of the microtitration plates used was also examined. Results indicated that the use of stabilized antigens is feasible, and these antigens offer the advantage of being ready for immediate use.