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ORIGINAL ARTICLE Table of Contents  
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Seroprevalence of syphilis in human immunodeficiency virus patients with special reference to diagnostic utility of rapid plasma reagin test

 Department of Dermatology, Venereology and Leprosy, Mamata Academy of Medical Sciences, Hyderabad, Telangana, India

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Date of Submission17-Aug-2022
Date of Decision04-Oct-2022
Date of Acceptance20-Oct-2022
Date of Web Publication02-Dec-2022


Background: Syphilis is a sexually transmitted infection caused by Treponema pallidum. High prevalence of syphilis was observed among human immunodeficiency virus (HIV)-positive patients. Atypical serological responses such as high antibody titers leading to frequent false-negative reactions have been reported with nonspecific treponemal tests. Simultaneous infection of syphilis and HIV in pregnant women increases the risk of HIV transmission from mother-to-child.
Aim: The aim of the study was to assess the seroprevalence of syphilis in HIV patients including pregnant women and to know the efficiency of serological tests in detecting syphilis among HIV patients.
Materials and Methods: The present study was a hospital-based cross-sectional study conducted among 500 HIV-reactive patients, including 100 HIV-reactive pregnant women attending the Outpatient Department of Dermatology, Venereology and Leprosy in a tertiary care center were enrolled in the study and were tested for the presence of syphilis using rapid plasma reagin (RPR) and T. pallidum hemagglutination assay (TPHA).
Results: Among 500 samples, 58 (11.65%) were positive for syphilis. The most common age group was 30–39 years. Both RPR and TPHA were reactive in 25% of cases, TPHA reactive in 60.2% of cases, and only RPR reactive in 14.7% of cases. Seropositivity among pregnant women was 7%. The sensitivity and specificity of RPR test was 29.3% and 97.7%, respectively, in comparison with TPHA. Positive and negative predictive values of the same were found to be 62.9% and 91.3%, respectively, compared to TPHA.
Conclusion: In all symptomatic and asymptomatic cases of syphilis, both RPR and TPHA should be performed for laboratory diagnosis of syphilis. It is advocated that all patients with newly diagnosed HIV should be suggested for syphilis serology and vice versa.

Keywords: Human immunodeficiency virus, rapid plasma reagin, syphilis, Treponema pallidum hemagglutination assay

How to cite this URL:
Lakshminarayan D, Vodapalli AK, Kolla SH, Nakka AR. Seroprevalence of syphilis in human immunodeficiency virus patients with special reference to diagnostic utility of rapid plasma reagin test. MRIMS J Health Sci [Epub ahead of print] [cited 2023 Oct 4]. Available from: http://www.mrimsjournal.com/preprintarticle.asp?id=362536

  Introduction Top

Syphilis is a systemic disease caused by Treponema pallidum. It is well known for its protean nature with a spectrum of asymptomatic infections to florid systemic affliction. Varied manifestations make this infection difficult to identify and thus it has been a challenging public health problem. Moreover, the prevalence of syphilis varies significantly among various regions of the same country as well as the various subgroups of the population studied. Human immunodeficiency virus (HIV) pandemic had added even more complexity to the already existing complex problem by increasing the risk of acquiring syphilis, variability in clinical presentations, frequent unusual serological responses such as high titers and false-negative reactions with nonspecific treponemal tests.[1]

Simultaneous infection of syphilis and HIV in pregnant women increases the risk of HIV transmission from mother-to-child.

Epidemiological studies of syphilis are few in the Indian Subcontinent with incidence rates of 5.4% in an STI clinic-based study to a prevalence of 21.9% in a cohort study on long-distance truck drivers.[2],[3]

Indian studies on the prevalence of syphilis among the HIV population are even rare with zero percent in a study based on the venereal disease research laboratory (VDRL) alone whereas the same was found to be 11.1% from another study based on both T. pallidum hemagglutination assay (TPHA) and VDRL.[4],[5]

The present study was done to assess the seroprevalence of syphilis in HIV patients including pregnant women and to know the efficiency of serological tests in detecting syphilis among HIV patients.

  Materials and Methods Top

The present study was hospital-based cross-sectional study conducted among HIV-reactive patients, including HIV-reactive pregnant women attending the outpatient department of dermatology, venereology and leprosy in a tertiary care center located in urban area. A total of 500 HIV-reactive patients, including 100 HIV-reactive pregnant women were included in the study by convenient sampling method. The study period was 18 months. All the HIV-reactive patients enrolled during this period and those who had given informed consent were included in the study. Those who were not willing to participate were excluded from the study.

Data were collected using semi-structured questionnaire after obtaining institutional ethical committee approval and after taking written informed consent from the study subjects. The questionnaire includes a detailed history regarding patient's age, sex, occupation, marital status, mode of acquisition of HIV, CD4 count, high-risk behavior, genital ulcer or rash in the past, recurrent abortions, still births in females, prior history of diagnosis or treatment for syphilis is taken for each patient. Blood samples were drawn from these patients for which both rapid plasma reagin (RPR) and TPHA were done on all samples and the results were analyzed.

All the subjects underwent a complete general, genital, mucosal, and systemic examination to actively rule out other sexually transmitted infections and were treated as per Centers for Disease Control and Prevention guidelines.[6]

Statistical analysis was done using IBM Statistical Package for the Social Sciences statistics, version 20. Data was presented in the form of numbers and percentages for categorical variables. Sensitivity and specificity were calculated accordingly.

Rapid plasma reagin

The RPR test was carried out qualitatively for all the samples and titration was done only on reactive samples. A standard RPR test with 18 mm circle card was performed, by mixing one drop of serum with one drop of RPR reagent, on a rotary RPR shaker for 8 min, and results read in good light. Macroscopically, visible black clumps against a white background on card indicates reactive sample whereas those appear to have smooth uniform light gray color indicates nonreactive samples. Results were recorded as reactive and nonreactive with respect to positive and negative control sera which were carried out in each test run.[5] Sensitivity of RPR is 86% and specificity is 98%.[5]

Treponema pallidum hemagglutination assay

TPHA is a passive particle agglutination assay for the qualitative and semiquantitative detection of antibodies to T. pallidum in human serum and plasma. TPHA test was performed by adding 2–3 drops of serum to the sample well using a disposable sample dropper. Results were noted within 5 min–15 min. Results were interpreted as positive, if there were two colored bands one at test region and another at control line region and negative if there was only one color band at control line region. Sensitivity of TPHA is 99.9% and specificity is 99.5%.[5]

  Results Top

Among 500 HIV-reactive patients, 58 patients were seropositive for syphilis with TPHA accounting for a prevalence of 11.6% [Table 1].
Table 1: Prevalence of seropositivity of syphilis with Treponema pallidum hemagglutination assay and rapid plasma reagin

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Among 500 patients, RPR was reactive in 27 (5.4%). Out of 27, only 17 (3.4%) correlated with TPHA. The rest ten RPR results were false positive. Hence, the seroreactivity of syphilis with RPR is 3.4% [Table 1] and [Table 2].
Table 2: Correlation of rapid plasma reagin and Treponema pallidum hemagglutination assay among human immunodeficiency virus-positive patients

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Of 500 patients, 225 (45%) were male and 275 (55%) were female. Among males, 40 (17.77%) were seropositive for syphilis. Among females, 18 (6.54%) were seropositive for syphilis. Thus, the seroprevalence was more in males than in females with a male-to-female ratio of 2.2:1. The difference was statistically highly significant with a P < 0.001 [Table 3].
Table 3: Sociodemographic distribution of study subjects

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Among 58 syphilis patients, the most commonly affected age group was 30–39 years (51.72%) followed by 20.6% in each group 20–29 years and 40–49 years [Table 3].

High seroprevalence was seen in truck drivers 23 (39.6%) followed by manual labor 20 (34.48%), unemployed 13 (22.4%), and least seroprevalence was seen among farmers 2 (3.44%) [Table 3].

Out of 58 syphilis patients, 48 (82.75%) were married, 6 (10.34%) were unmarried, and 4 (6.89) were divorced.

Majority of patients were asymptomatic 45 (77.58%), 10 (17.24%) presented with rash of secondary syphilis, 3 (5.17%) presented with genital ulcer (primary chancre) [Table 4].
Table 4: Seropositivity of syphilis in relation to clinical presentation and CD4 count

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Majority of syphilis patients, 40 (68.9%) had CD4 in the range of 201–500, 13 (22.41%) had CD4 <200, and 5 (8.62%) had CD4 >500 [Table 4].

The sensitivity, specificity, positive and negative predictive values of RPR were 29.3%, 97.7%, 62.9%, and 91.3% compared to TPHA, respectively.

In our study, out of 58 syphilis patients, RPR test done without dilution could only detect 17. When performed serial dilutions, all 58 patients were found to be positive. Hence, negative RPR may not rule out syphilis in patients with HIV infection [Table 2].

In the present study, 10 cases were false positive with RPR test which indicates a high false positivity rate [Table 2].

Among 100 pregnant women, seroreactivity with TPHA was seen in seven cases (7%). RPR positivity was seen in four out of 100 pregnant women but only two of these were reactive with TPHA giving a prevalence of 2% with RPR. Among seven syphilis-positive antenatal women, majority of them were observed in the age group of 20–29 years (six cases; 85.71%). Among seven seropositive antenatal women, five (71.42%) were doing manual labor; two were homemakers (28.57%). Majority of seropositive antenatal women were having CD4 in the range of 201–500 (six cases; 85.71%).

  Discussion Top

As syphilis is a disease with broad range of manifestations and variable courses, assessing reports of unusual clinical or laboratory findings in the HIV-co-infected patients is difficult. Serological tests may be difficult to interpret in HIV seropositive patients because of atypical responses such as delayed responses to both treponemal and nontreponemal tests. The clinical manifestations, serological responses, efficacy of treatment, and occurrence of complications of syphilis may be altered in patients co-infected with HIV.

A total number of 500 HIV-reactive patients with age group ranging from 15 to 65 years were included in the present study. This includes 100 HIV-reactive pregnant women. Among 500 patients, 225 (45%) were male and 275 (55%) were female. The mean age of patients in the study group is 33.6 years. Most of them were married. All were heterosexuals and sexually active.

Seropositivity of syphilis in our study was 11.6% among HIV patients. This nearly correlates with the study done by Muñoz-Pérez et al.[7] which had reported a seroprevalence of 13%. The seroprevalence of syphilis in HIV-reactive patients varied from 1% to 59.7% among various studies. The tests employed and the sample size is not same in all these studies.[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20]

Seropositivity of syphilis with RPR was only 3.4% whereas the seropositivity with TPHA was 11.6%. In the present study, the seroprevalence of syphilis was more with TPHA than with RPR, similar to a study by Turbadkar et al.[8] where 47.7% of patients were positive with TPHA and 9.1% of patients were positive with VDRL.

TPHA reactivity among pregnant women was 7%. This was found to be similar to a study by Potter et al.[9] which reported seropositivity of 7% among HIV-reactive pregnant. RPR done on a routine in these patients revealed a positivity of 4% out of which only two were also positive for TPHA giving a prevalence of 2% with RPR. Out of 7 pregnant women found to be seropositive for syphilis only two could be detected by RPR. This stresses the need to perform a specific treponemal test for syphilis. The importance of highlighting the seropositivity among pregnant women is that the load of undetected cases could be identified and congenital syphilis can be prevented or serious sequelae of syphilis can be reduced if this group is adequately treated.

In the present study, high seroprevalence was noted among the age group of 30–39 years (51.72%) followed by 20–29 years and 40–49 years which showed a prevalence of 20.69%. Among 100 pregnant women tested, 85.71% seropositivity was seen in the age group of 20–29 years.

The seroprevalence of syphilis in HIV patients in our study is more in males (17.77%) than in females (6.54%). The difference is found to be highly statistically significant. This correlates with a study by Griemberg et al.[10] where the prevalence of syphilis HIV co-infection was significantly higher in males (13.6%) compared to females (1.7%).

In the current study, we noticed that among those found positive for coinfection, Truck drivers were found to have a high seroprevalence (39.65%) followed by manual labor accounting for 34.48%. 15.52% were homemakers, 6.90% were unemployed, and least seroprevalence was seen among farmers 3.45%. Among pregnant women, manual labor accounted for 71.43% of seropositives and 28.57% were homemakers among which a higher proportion of patients (82.76%) were married. Unmarried patients accounted for 10.34% and divorced for 6.89%. Among HIV-reactive pregnant women, all syphilis seropositive women were married. CD4 count was evaluated among those found positive for syphilis HIV co-infection. 68.97% of patients had CD4 in the range of 201–500 followed by 22.41% with CD4 <200.8.62% of patients had CD4 >500. Among pregnant women, 85.71% showed CD4 counts in the range 201–500.

Clinical expertise alone may be insufficient to guide treatment decisions in the presence of undetected co-infection,[21],[22] resulting in missed case detection, incomplete or partial treatment, and suboptimal clinical follow-up. The present study noticed a high proportion (77.59%) of asymptomatic syphilis patients. A study by Seña et al.[23] showed 55% of co-infected patients were asymptomatic. The importance of screening asymptomatic HIV-reactive patients for syphilis was highlighted in a study by Cohen et al.[24] and Winston et al.[25]

In the present study, 17.24% presented with rash of secondary syphilis. Among rash of secondary syphilis, high incidence of maculopapular rash was seen in our patients. This is similar to the study by Seña et al.[23] which reported a high incidence of maculopapular syphilis. Corymbose lesions were seen in one patient, psoriasiform lesions were present in two patients. Condyloma lata was seen in four patients. Although literature reports increased incidence of malignant syphilis in HIV-reactive patients, no case of malignant syphilis was seen in our study. Genital ulcer suggestive of primary chancre was noticed in 5.17% of the subjects.


Our study had several limitations. First, it is a hospital-based study which might not be a true representation of the community at large. Second, the sample size and study period will be reflecting a short-term trend. A large sample size and long-term studies are required to get more accurate data.

  Conclusion Top

For all suspected cases of syphilis, performing two serological tests (RPR and TPHA) significantly improves the detection rate of syphilis. There is also a need to perform serial dilutions in every case of nonreactive RPR.

The present study noticed a high percentage of asymptomatic patients, who were detected by positive serological tests. Early detection of asymptomatic patients prevents the development of unpleasant clinical sequelae of syphilis and also reducing their period of infectiousness. Thus, it is recommended that all patients with newly diagnosed syphilis should be counseled for HIV testing and similarly serological testing for syphilis should be carried out in every patient with newly diagnosed HIV infection.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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Correspondence Address:
Annie Ratnam Nakka,
9-1-45, Churchpet, West Godavari, Narsapur - 534 275, Andhra Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/mjhs.mjhs_80_22


  [Table 1], [Table 2], [Table 3], [Table 4]


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