Biologic False-positive Research Articles

COMPARISON STUDY OF SEMI-QUANTITATIVE RPR TEST AND TPHA FOR SERODIAGNOSIS OF SYPHILIS AT A TERTIARY CARE HOSPITAL, UDAIPUR, RAJASTHAN

Areactive RPR should always be conrmed with treponemal test like TPHAin suspected syphilis patients to rule out biological false positive cases. It is important to nd an alternative to TPHA as it is frequently not available in resource limited health care facilities of developing nations like India. Aim:Aim of our study is to evaluate semi-quantitative RPR test and TPHAin serological diagnosis of syphilis in resource limited health care facilities. Methodology: A retrospective cross sectional study from January 2020 to December 2021 was conducted on 116 suspected cases of syphilis. All cases were tested for qualitative RPR test, semi-quantitative RPR test ant TPHA test. Serum samples that are positive in qualitative RPR test but negative in TPHAwere referred to as biologic falsepositive (BFP) reactions. Results:We found 32 (27.58%) biological false positive (BFP) cases in dilutions 1:8 or below on semi quantitative RPR test. No BFP case was found in dilutions 1:16 or more. BFP can occur in any age group. We have noted that female 25(21.55%) were showing more BFP cases in our study. Conclusions: No biological false positive reaction has been found in above 1:8 dilution of RPR test. Semi-quantitative RPR test results in 1:16 or more dilution is equivalent to TPHAresults for diagnosis of syphilis.

The Impact of Combined Antiretroviral Therapy on Biologic False-Positive Rapid Plasma Reagin Serologies in a Longitudinal Cohort of HIV-Infected Persons

Our objective was to determine the impact of combination antiretroviral therapy (cART) and the degree of immunosuppression on biologic false-positive (BFP) rapid plasma reagin (RPR) tests among persons infected with human immunodeficiency virus (HIV). This was a nested retrospective study of HIV-infected patients enrolled in the Johns Hopkins HIV Clinical Cohort. BFP RPR was defined as a reactive RPR and a nonreactive fluorescent treponemal antibody-absorption (FTA-ABS) test. Patients with BFP tests were compared to 2 control groups: HIV-infected patients (1) with active syphilis (reactive RPR and FTA-ABS) and (2) without current syphilis (nonreactive RPR). A persistent BFP test was defined by having at least 2 visits with consistent BFP at all visits. Of 711 patients with HIV, 96 (13.5%) had BFP tests and 342 (48.1%) had syphilis. Twenty-two of 96 (23%) had persistent BFP tests. cART use was associated with decreased odds of BFP tests compared to having syphilis (adjusted odds ratio [AOR], 0.31; 95% CI, .15-.63) and those with nonreactive RPR (AOR, 0.42; 95% CI, .22-.81). cART use was also associated with decreased odds of BFP persistence (AOR, 0.07; 95% CI, .01-.33). Neither CD4 count nor HIV RNA was significantly associated with BFP test results. Lower RPR titers, younger age, and injection drug use were associated with increased odds of BFP. The use of cART appears to decrease the odds of BFP RPR tests. This finding suggests that nontreponemal titer fluctuations in persons with HIV may reflect the influence of factors unrelated to syphilis disease activity.

P2.069* Factors Associated with Biologic False Positive Rapid Plasma Reagin (RPR) Serologies in HIV-1-Infected Persons

ObjectivesThe prevalence of biologic false-positive (BFP) non-treponemal tests ranges from 4–15% among HIV-infected persons. Abnormalities in B cell function are hypothesised to increase the probability of BFP in this population....

Hepatitis C virus infection and biological falsepositive syphilis test: a single-center experience

Rapid plasma regain positive and/or treponema pallidum hemagglutination negative [RPR(+)/TPHA(-)] results were designated as biologic false-positive (BFP). There are limited data about BFP reactions against syphilis in patients with hepatitis C virus (HCV) infection. This study aimed to determine the prevalence of BFP reactions for syphilis in patients with HCV infection in a large sample and assess the relationship between BFP reactions and HCV infection. A total of 2656 patients with positive anti-HCV and 5600 healthy control subjects were enrolled in this study. Hepatitis C serology was determined by a second generation ELISA test for HCV antibody. Syphilis serology was determined by the RPR test. Those subjects with reactive RPR positive underwent the TPHA test. Demographics and laboratory data were collected by trained clinicians. Among 2656 patients, 111 (4.2%) had a reactive RPR test. Of the 111 patients who were subjected to reactive RPR test, 30 (27.0%) showed HCV(+)/RPR(+). Of 5600 healthy controls, 80 (1.4%) had a reactive RPR test. Fourteen (17.5%) controls with HCV(-)/RPR(+) had a non-reactive TPHA test. These represented 1.1% of all HCV-positive and 0.3% of all HCV-negative subjects (P<0.001). A significantly increased prevalence shown by false-positive tests for syphilis was observed in elderly HCV-seropositive patients. BFP-HCV positive group had a higher prevalence of eosinophilia. The eosinophil abnormality was compared between the patients and controls (66.7% vs 21.4%, P=0.0043). No significant results were observed in antinuclear antibodies, antiphospholipid and complement (C3, C4) (P>0.05). The data of this study demonstrate that HCV infection is associated with a false-positive RPR test. In this study BFPs were significantly more common in HCV positive patients compared to HCV-negative ones. Eosinophil abnormality can be considered as a predictor for BFP. Excessive BFPs must be considered in assessing the frequency of syphilis in a HCV-positive population and the importance of the treponemal specific serologic test should be emphasized for a diagnosis of syphilis in such population.

7B.1 Pathogenesis of the antiphospholipid syndrome (APS)

The APS is a thrombophilic condition that is identified by phenomenologic surrogate tests that were derived from the biologic false positive (BFP) syphilis test and the paradoxical “lupus anticoagulant” (LAC) phenomenon, described about 50 years ago [1]. Current diagnosis of the syndrome requires that the patients have clinical manifestations such as thrombosis and/or spontaneous pregnancy losses and at least 1 positive test that is confirmed at least 12 weeks later [2]. The major antigenic target for “antiphospholipid” antibodies is b2-glycoprotein I (b2GPI), a phospholipid-binding protein that is a member of the short-chain consensus repeat (SCR) superfamily. The protein has a “J” shape and is composed of an extended chain of 5 SCR domains. The structure of SCR domain V deviates from the standard fold of the 4 other domains and contains the putative phospholipid-binding site [3]. It has recently been reported that IgG antibodies recognizing an epitope in domain I of b2GPI consisting of Gly40 Arg43 have LAC activity and are strongly associated with thrombosis [4]. Several mechanisms have been proposed to explain how antiphospholipid antibodies might cause susceptibilities to pregnancy losses and to thrombosis [1]. Among these are mechanisms that affect platelet function, prostaglandin synthesis, endothelial cell signaling, apoptosis, effects on protein C and S activities, the endothelial protein C receptor, protein Z function and antiphospholipid antibody-mediated activation of complement with subsequent release of TNF-alpha, and the antiphospholipid antibodymediated disruption of annexin A5 (AnxA5) discussed below. AnxA5 is a potent anticoagulant protein whose anticoagulant properties are a consequence of its high affinity for anionic phospholipid [5,6]. The protein forms 2-D crystals on phospholipid surfaces [7 9] that shield the phospholipid from availability for the critical phospholipid-dependent coagulation reactions. AnxA5 forms noncovalent polymers by forming trimers [7 9], and then trimers of the trimers over phospholipid bilayers. Figure 1 shows a colorized lower power AFM image of the crystal array, demonstrating the highly ordered screen-like structure; panel B shows a higher power detail of this array, with the central space filled with an individual trimer; panel C shows 6 trimers (the thin black circle delineates 1 trimer) that are arrayed in a hexagonal configuration. These 2-D arrays shield phospholipids from availability for the phospholipiddependent coagulation reactions. Fig. 1.

Syphilis serology in human immunodeficiency virus infection: evidence for false-negative fluorescent treponemal testing.

Injection drug users were assessed serologically for human immunodeficiency virus infection and syphilis every 6 months. Treatment histories were reviewed for any high-titer biologic false-positive (BFP) reactors, that is, persons with rapid plasma reagin (RPR) titers > or = 1:4 and negative results for fluorescent treponemal antibody absorption (FTA-ABS) tests. Selected sera were analyzed further by immunoblotting for the presence of antibodies reactive with specific Treponema pallidum antigens. Of 112 BFP reactors, 35 (31%) had at least one RPR test reactive at a dilution >1:8 while the FTA-ABS test remained nonreactive. Five reactors (4.5%) converted from nonreactive to reactive by FTA-ABS test; 4 (3.6%) were reactive by FTA-ABS tests but later became nonreactive. Antibodies to T. pallidum membrane antigens were detected in some samples that were persistently nonreactive by FTA-ABS test. Serologic patterns over time, along with very high-titer BFP reactions and reactivity with T. pallidum-specific antigens, suggest that some BFP reactions may represent FTA-negative syphilis.

Lupus anticoagulant in systemic lupus erythematosus: a clinical and renal pathological study.

Circulating lupus anticoagulant (LA) is associated with thrombosis in large and small vessels. To determine how often the presence of LA is associated with thrombosis within the renal microcirculation, 33 patients with systemic lupus erythematosus (SLE), renal dysfunction, and LA were identified over a 25-year period (LA group) and 32 patients with renal SLE but with normal gross coagulation screen were matched for age, sex, and biopsy timing (C group). Prevalences of serositis, neuropsychiatric illness, leukopenia, thrombocytopenia, hemolysis, anti-DS-DNA elevation, and complement reduction were similar. Arthritis was less and biologic false-positive (BFP) syphilis serology more common in LA. More LA patients had thrombotic events (LA 39% v C 13%; P = 0.014); bleeding episodes, including postbiopsy, were similar. At biopsy, hypertension (LA 55%, C 41%), serum creatinine (mean +/- SD: LA 186 +/- 168 mumol/L [2.1 +/- 1.9 mg/dL] v C 150 +/- 168 mumol/L [1.7 +/- 1.9 mg/dL]) and proteinuria (LA 2.6 +/- 3.1 g/24 h v C 3.1 +/- 2.7) were similar. Lesions by World Health Organization (WHO) class, activity, and chronicity indices, as well as immunofluorescence (IF) and electron microscopy (EM) findings, were not significantly different. Occlusive glomerular, arteriolar, and arterial fibrin thrombi, along with varying degrees of renal thrombotic microangiopathy, were seen in five of 33 patients with LA, but zero of 32 C patients (P = 0.053); three of these five patients died soon after biopsy. Overall, mortality was not different between LA and C. We conclude that the majority of patients with SLE, renal dysfunction, and LA exhibit renal morphologic findings indistinguishable from patients without LA. However, a significant minority of LA patients have thrombotic microangiopathy in their biopsy, which is accompanied by a worse prognosis.

Association of biologic false-positive reactions for syphilis with human immunodeficiency virus infection.

The prevalence of biologic false-positive (BFP) reactions for syphilis (reactive rapid plasma reagin [RPR] test, nonreactive fluorescent treponemal antibody absorption [FTA-ABS] test) among patients attending two sexually transmitted disease (STD) clinics was evaluated to assess relationships between BFP reactions and human immunodeficiency virus (HIV) infection. Among 4863 patients, 357 (7.3%) had serologic evidence of syphilis and 4.9% had HIV infection. Only 40 patients (0.8% of total patients, 11% of those with reactive RPR tests) had BFP serologic tests for syphilis. There were no demographic differences between true syphilis and BFP patients as to sex, age, or intravenous drug use. BFP patients tended to have lower RPR titers (less than or equal to 1:4) than did true syphilis patients. After excluding 317 patients with reactive FTA-ABS tests, BFP RPR tests were seen in 6 (4%) of 159 HIV-seropositive patients and 34 (0.8%) of 4387 HIV-seronegative patients (odds ratio, 5.0; 95% confidence interval, 1.9-12.7). Although more common among HIV-infected than HIV-uninfected patients, BFP reactions are relatively rare among STD clinic patients, and 89% of patients with reactive RPR or VDRL serologic tests for syphilis had current or prior syphilis infection. The RPR test remains useful for guiding decisions regarding therapy for syphilis.

Circulating Anticoagulant in the Procainamide-Induced Lupus Syndrome

An elderly man with procainamide hydrochloride-induced lupus syndrome had a circulating anticoagulant against factor XI and a biologic false-positive (BFP) test result for syphilis. This was not associated with hemorrhagic problems. The activity of the circulating anticoagulant and the BFP disappeared within days following discontinuation of procainamide and the administration of corticosteroids.

Circulating anticoagulant in the procainamide-induced lupus syndrome

An elderly man with procainamide hydrochloride-induced lupus syndrome had a circulating anticoagulant against factor XI and a biologic false-positive (BFP) test result for syphilis. This was not associated with hemorrhagic problems. The activity of the circulating anticoagulant and the BFP disappeared within days following discontinuation of procainamide and the administration of corticosteroids.

Biologic false-positive reactions in serologic tests for syphilis in narcotic addiction. Reduced incidence during methadone maintenance treatment.

Biologic false-positive (BFP) tests for syphilis was found in 23% of 69 New York heroin addicts. After 23 ± 7 months of methadone maintenance treatment, BFP decreased to 5.8%. No correlation between abnormalities in SGOT, alkaline phosphatase, albumin, total protein, and the presence or loss of BFP reactions was observed. Similarly, no correlation between serum IgM or IgG levels or latex-fixation titers and the presence or loss of BFP reactions was found. BFP is a nonspecific serologic abnormality seen in urban narcotic addicts, which is alleviated by methadone treatment, presumably as a result of reduced exposure to unknown antigens.

Familial Chronic Biologic False-Positive Seroreactions for Syphilis

Two families manifested hereditary chronic biologic false-positive (BFP) seroreactions for syphilis. In one family, this trait was demonstrated in four of seven members, affecting three generations, grandfather, son, daughter, and granddaughter. Grandfather and son manifested increasing reagin titers over a period of 11 to 17 years. Positive Coombs' tests indicating autoantibodies were demonstrated in two seroreactors. In the second family, three of five members were affected, father, son, and daughter. The chronic BFP reaction appears to be a genetically transmissible trait associated with humoral autoantibodies with the potential for autoimmune disease.

Familial chronic biologic false-positive seroreactions for syphilis. Report of two families, one with three generations affected

Two families manifested hereditary chronic biologic false-positive (BFP) seroreactions for syphilis. In one family, this trait was demonstrated in four of seven members, affecting three generations, grandfather, son, daughter, and granddaughter. Grandfather and son manifested increasing reagin titers over a period of 11 to 17 years. Positive Coombs' tests indicating autoantibodies were demonstrated in two seroreactors. In the second family, three of five members were affected, father, son, and daughter. The chronic BFP reaction appears to be a genetically transmissible trait associated with humoral autoantibodies with the potential for autoimmune disease.

Biologic False-Positive Reactions for Syphilis

To the Editor:— The problem posed ( 203 :996, 1968) regarding a 54-year-old housewife with a reactive fluorescent Treponemal antibody test merits an expanded discussion particularly of the possibility of a biologic false-positive (BFP) reaction. Syphilis is the great mimic, and we of the Osler tradition recall, "When it comes to syphilis, suspect your grandmother." The experienced physician, however, occasionally finds a positive reaction he is forced to classify as BFP. Garson, 1 after an excellent discussion of the tests for syphilis developed before 1959, said: "No serologic test for syphilis diagnoses syphilis; rather it informs us of the immunologic status of the patient in relation to the antibody being treated. None... is absolutely specific for syphilis alone." In Current Diagnosis (1966) Beerman 2 points out the possibility of reactivity not only in syphilis and related treponemal diseases such as "yaws, pinta, or beje," but also in various other states such

The Appearance and Persistence of VDRL, RPCF, and TPI Antibody during the Course and Treatment of Experimental Syphilis in the Rabbit

A knowledge of the appearance and persistence of VDRL, RPCF, and TPI antibody during the course and treatment of syphilitic infection has become increasingly important with the development and general acceptance of the “triple test plan” for the serologic diagnosis of syphilis (1). The plan is designed primarily to aid the physician in differentiating biologic false positive (BFP) reactors from latent syphilitics. The VDRL test is used as a preh'minary#screening procedure for patients with no history or clinical manifestations of syphilitic infection. A non-reactive result is accepted as evidence for the absence of syphilis while reactive or weakly reactive sera are subjected to the RPCF test. A corroborative reactive or weakly reactive RPCF result is considered evidence for past or present infection with Treponema pallidum, while a non-reactive result necessitates the performance of a TPI test. If the TPI test is reactive, past or present infection is indicated; a non-reactive result signifies a BFP reaction.

Auto-immune disease and the chronic biologic false-positive test for syphilis.

A significant percentage of persons who react positively to serological tests for syphilis (STS) do not have syphilis but are referred to as chronic biologic false-positive (BFP) reactors. The author studied 192 BFP reactors. Most of them were apparently healthy and had submitted to the STS in the course of premarital, prenatal, or preemployment examinations, but others had various diseases, including two cases of systemic lupus erythematosus (SLE). The clinical course of these BFP reactors has been significant, since the group includes 14 who now have SLE and 3 who have since developed Hashimoto's thyroiditis. The marked predominance of women in this series of BFP reactors was not explained by any discernible bias in the sample.

False-Positive Reactions Among Narcotic Addicts

To the Editor:— I have noted the article inThe Journal, Jan. 28, 1961, entitled Biologic False-Positive Reactions for Syphilis Among Narcotic Addicts, in which the following sentence appears: The high proportion of non-reactive TPI tests among narcotic addicts with no history of syphilis and reactive STS provides direct evidence that certain drugs may induce BFP reactions. Unless other possible causes were thoroughly investigated, I wonder whether the conclusion that drugs have been demonstrated to cause biologic false-positive (BFP) reactions is justified. I should think the wording might be changed somewhat as follows: The high proportion of non-reactive TPI tests among narcotic addicts with no history of syphilis and reactive serologic test for syphilis ( STS ) is perhaps explained by the fact that addicts are subject to a number of conditions which are known to cause BFP reactions: viral hepatitis, malaria, and others. It may also be hypothesized that the chronic

Biologic False-Positive Reactions for Syphilis Among Narcotic Addicts

PRIOR to 1949, the occurrence of a reactive serologic test for syphilis (STS) in the absence of a history of lesions of the disease had been considered to be of equivocal significance by many investigators. In that year, the specific Treponema pallidum immobilization (TPI) test was developed by Nelson and Mayer 1 thus making available an accurate procedure for the differentiation of biologic false-positive (BFP) reactions from those due to infection with T. pallidum . Subsequently, numerous diseases and conditions have been observed to show BFP reactions, including collagen diseases, 2 pregnancy, 3 Brucella infection, and many others. During the past few years, increasing attention has been focused on the problem of narcotic addiction. Concomitant with this interest, it was observed that sera from many patients addicted to narcotics showed reactive STS. This report presents the incidence of BFP reactions among such individuals as measured by the TPI test. Methods

Experience with VDRL Flocculation Antigen in the Kolmer Complement Fixation Test

IN RECENT years interest has been concentrated on treponemal antigens and little attention has apparently been given to improvement of the currently available nontreponemal antigens. This is unfortunate, since an easily available lipoidal antigen with improved specificity would be of extreme value in the laboratory. In the United States, with its premarital and prenatal laws, millions of serologic tests for syphilis are performed on presumably healthy individuals. All too frequently, particularly with cardiolipin antigens commercially available, reactive laboratory findings are obtained which are not supported by clinical findings. Various estimates of biologic false positive reactions with routine procedures have been advanced by various authors. Variation in these figures is wide. They, of course, are influenced by the type of population group evaluated, the serologic procedures and type of antigen employed, and the definition of positivity used. Deservedly or not, the current criterion of the value of a serologic test for syphilis is its sensitivity and specificity in comparison with the sensitivity and specificity of the Tbreponema palliduim immobilization (TPI) test of Nelson and Mayer. Using the TPI test as a reference, rather high false positive figures have been found with standard lipoidal antigens. MacPherson, Ledbetter, and Martens (1) reported results of 21 to 40 percent of routine reactive tests as biologic false positives, and a number of other authors, including Moore and Lutz (2), reported 40 percent false positives, In a comparative study of 572 serums which were reactive with nontreponemal tests, Wilkinson (3) found that the Kahn test gave 17 percent nonspecific reactions, the Wassermann test with lipoidal antigen 13 percent, and the Wassermann test with cardiolipin antigen 23 percent. In 244 patients found to be seropositive on routine testing during pregnancy, blood tests of 27.5 percent gave presumed nonspecific reactions. In our own laboratory, of 796 reactive VDRL slide tests, 435, or 54.6 percent, were assumed to be biologic false positives, with the TPI test used as the reference test. Of 724 reactive cardiolipin Kolmer tests, 385, or 53.2 percent, were in the same category. These figures were obtained on specimens submitted to us for TPI tests, and these cases can consequently be placed in the problem category.

Serodiagnosis with antigens of Treponema pallidum in lupus erythematosus.

Lupus erythematosus of the fixed variety rarely presents difficulties to the trained observer. Until recently, the same could not be said regarding the generalized or systemic form of the disease now generally designated as disseminated or systemic lupus erythematosus (SLE). It is only with the introduction of the newer laboratory aids that formerly obscure conditions have been properly identified and classified as belonging to a group of systemic diseases of which systemic lupus erythematosus is perhaps the most important and the commonest member. The early detection of SLE has been made possible by the L. E. phenomenon and the correct interpretation of the biologic false-positive (BFP) reaction that are observed in this disease. The relatively high incidence of systemic lupus erythematosus noted in recent years is probably not due to an actual increase in the number of cases but to better diagnosis from the now available clinical