ICDDR,B: Publication, ICDDR,B Periodicals, Screening for Syphilis in Routine Antenatal Care

Screening for Syphilis in Routine Antenatal Care

Summary. Screening for syphilis was carried out among 1,103 women; 80% were screened in their late 2nd trimester or during the third trimester. The prevalence of syphilis was 1.5%. A comparison of results of testing done by paramedics with those from a reference laboratory, showed that the sensitivity of the test when carried out by paramedics was only 13%. Screening for syphilis as currently carried out by paramedics is unreliable. Simpler diagnostic tests that could more easily be carried out by paramedics are needed for ante-natal screening using paramedics to be effective.

In Bangladesh, the prevalence of syphilis in groups vulnerable to HIV infection is high (1), but insufficient information exists on the prevalence of syphilis infections in pregnant women in the general population. The effects of untreated syphilis on pregnancy include spontaneous abortion, stillbirth, pre-maturity and congenital syphilis (2). Congenital syphilis has a wide array of serious manifestations, including meningitis and meningovascular syphilis. To effectively prevent foetal wastage and congenital anomalies, appropriate treatment must be given by first or early second trimester of pregnancy.

In a study carried out in rural Bangladesh, the prevalence of syphilis was about 1% in women with symptoms related to the genital tract (3). In contrast, a study among Dhaka slum dwellers revealed that more than 11% of men and 5% of women had syphilis (4). Another recently-published study estimated the prevalence of syphilis among female clients attending a basic healthcare clinic to be about 3% (5).

Most women with syphilis neglect to seek medical care, probably because the primary lesions are often painless and not seen, since they are located inside the vagina or cervix. The secondary stage of syphilis is characterized by nonspecific signs and symptoms. Only serological tests for screening can assure detection of syphilis in women. Screening and treating pregnant women for syphilis was shown to be inexpensive and cost-effective, in a demonstration project in Lusaka, Zambia (6). Even in countries with seroreactivity rates lower than 1 per 1,000, syphilis screening in pregnant women is cost-effective (7).

There is lack of information on the prevalence of syphilis among pregnant women in Bangladesh. Several operational questions have not been addressed, such as is antenatal care (ANC) screening for syphilis functional and valid in primary healthcare (PHC)-level clinics, using existing providers for ANC, and is routine screening acceptable to clients? This report presents findings of a cross-sectional, clinic-based study addressing these queries, conducted at two urban primary healthcare-level clinics: Sher-e-Bangla Nagar Government Dispensary (GoD) at Agargaon Pucca Market and the Mirpur PSKP clinic, between November 1999 and March 2001. It included 1,206 pregnant women who attended either of the clinics for ANC. Most were less than 25 years old, 36% had no education. About half of the pregnant women resided in slum dwellings. All were married.

In addition to routine antenatal care, each of these pregnant women was offered a blood test for screening for syphilis. Ninety-one percent (1,103 women) agreed to be screened. Of them, 96% knew their gestational age; eighty percent were screened in their late 2nd trimester or 3rd trimester (Fig 1). Almost all of these women were at their first antenatal visit with the current pregnancy.

The rapid plasma reagin (RPR) test for syphilis screening was done twice on each of the collected specimens. First, paramedics in the study clinics performed the test, and then the RPR was done at ICDDR,B RTI/STI Laboratory, where the TPHA was also done as a confirmatory test for syphilis. Reference laboratory testing of specimens was carried out to provide a gold standard against which to evaluate the reliability and validity of RPR test performed by paramedics.

Based on the results from the reference laboratory, the prevalence of syphilis was 1.5%. The reliability of the paramedics was measured by comparing the RPR test results from the paramedics with those of the reference laboratory, and calculating the degree of statistical agreement. The results of RPR from the reference laboratory agreed with those tests conducted by paramedics in only 13% of women. The sensitivity and specificity of paramedic testing was 13% and 96%, respectively. Based upon these results, it is estimated that if the clinics were to rely on the paramedic RPR testing, 87% of infected women would not be identified and 4 percent of non-infected women would be incorrectly labelled, and treated, as positive. By contrast, the findings from confirmatory TPHA testing showed that virtually all infected women were correctly identified in the reference laboratory by RPR, with 2% of non-infected women incorrectly found to be positive.

Reported by: Sher-e-Bangla Nagar Government Dispensary, Agargaon, Dhaka; Progoti Samaj Kallyan Protisthan (PSKP) clinic, Mirpur, Dhaka; RTI/STI Laboratory, Laboratory Sciences Division (LSD) and Infectious Diseases Unit, Health Systems and Infectious Diseases Division (HSID), ICDDR,B

Supported by: US Agency for International Development (USAID)

Comment

The occurrence of syphilis in pregnant women, given the severity of its consequences, was found to be high (1.5%). Most started ANC at a point in their pregnancy too late to prevent congenital syphilis with conventional treatment. Treatment during the late second and in the third trimester greatly increases the risk of treatment failure (8). Alternative strategies that will result in earlier entry into ANC are needed and must be tested.

The majority of women accepted testing and appeared to understand what syphilis was. However, screening carried out by paramedics was found to be unreliable. Thus, the findings of this report suggest deficiencies in the antenatal syphilis-screening programme when carried out by paramedics at primary level healthcare clinics. Syphilis-screening is ongoing at 23 NSDP urban clinics. One potential solution would be to provide more extensive training for paramedics, and to monitor for quality assurance closely by periodically sending out a panel of sera to each of the clinics for assessment; such an approach would be expensive, unwieldy and difficult to carry out and sustain. Centralized testing at qualified reference laboratories would seem to be the preferred strategy.

It is essential to design strategies to implement improved syphilis screening. One option would be to use simpler treponemal specific-rapid diagnostic testing that would be more easily performed by paramedics. Over twenty companies now manufacture rapid simple treponema-specific tests that can be used on whole blood, serum, or plasma. The tests can be used in primary healthcare settings as they are stable at room temperature for months, require no equipment, and give visual readout in 8-15 minutes (9). Limited evaluation suggests that some have comparable performance to laboratory-based tests (10). Such a programme would also require counselling programmes and educational campaigns to promote earlier antenatal clinic attendance so that timely screening and management would be possible. Cost-benefit analyses through direct measurement of the effect of screening on the prevention of adverse pregnancy outcomes are needed.

References

1. Bangladesh. Ministry of Health and Family Welfare. National AIDS/STD Programme. HIV in Bangladesh: where is it going? Background document for the dissemination of the third round of national HIV and behavioural surveillance. Dhaka: National AIDS/STD Programme, Ministry of Health and Family Welfare, Government of Bangladesh, 2001.

2. Schulz KF, Schulte JM, Berman SM. Maternal health and child survival: opportunities to protect both women and children from the adverse consequences of reproductive tract infections. In: Germain A, Holmes KK, Piot P, Wasserheit JN, editors. Reproductive tract infections: global impact and priorities for womens reproductive health. New York: Plenum Press, 1992;145-82.

3. Hawkes S, Morison L, Foster S et al. Reproductive-tract infections in women in low-income, low-prevalence situations: assessment of syndromic management in Matlab, Bangladesh. Lancet 1999;354:1776-81.

4. Sabin K, Rahman M, Hawkes S et al. A cross-sectional study on the prevalence of sexually transmitted infections among Dhaka slum dwellers. In: Hawkes S, Qadri F, Rabbani GH et al., editors. ASCON VI: programme and abstracts of Sixth Annual Scientific Conference, 7-9 March 1997. Dhaka: International Centre for Diarrhoeal Disease Research, Bangladesh, 1997:21.

5. Bogaerts J, Ahmed J, Akhter N et al. Sexually transmitted infections among married women in Dhaka, Bangladesh: unexpected high prevalence of herpes simplex type 2 infection. Sex Transm Inf 2001;77:114-9.

6. Hira SK, Bhat GJ, Chikamata DM et al. Syphilis intervention in pregnancy: Zambian demonstration project. Genitourin Med 1990;66:159-64.

7. Stray-Pederson B. Economic evaluation of maternal screening to prevent congenital syphilis. Sex Transm Dis 1983;10:167-72.

8. Arya OP. Bacterial infections. In: Arya OP, Hart CA, editors. Sexually transmitted infections and AIDS in the tropics. Wallingford: CAB International, 1998:153-200.

9. Maybe D, Peeling RW. Rapid diagnostic tests for sexually transmitted infections. IPPF Med Bull 2002;36:1-3.

10. Fears MB, Pope V. Syphilis fast latex agglutination test, a rapid confirmatory test. Clin Diagn Lab Immunol 2001;8:841-2.

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Published: June 2003.