Maternal and congenital syphilis in Bolivia, 1996: prevalence and risk factors

OBJECTIVES

The present study was carried out in seven maternity hospitals to determine the prevalence of maternal syphilis at the time of delivery and the associated risk factors, to conduct a pilot project of rapid syphilis testing in hospital laboratories, to assure the quality of syphilis testing, and to determine the rate of congenital syphilis in infants born to women with syphilis at the time of delivery--all of which would provide baseline data for a national prevention programme in Bolivia.

METHODS

All women delivering either live-born or stillborn infants in the seven participating hospitals in and around La Paz, El Alto, and Cochabamba between June and November 1996 were eligible for enrolment in the study.

FINDINGS

A total of 61 out of 1428 mothers (4.3%) of live-born infants and 11 out of 43 mothers (26%) of stillborn infants were found to have syphilis at delivery. Multivariate analysis showed that women with live-born infants who had less than secondary-level education, who did not watch television during the week before delivery (this was used as an indicator of socioeconomic status), who had a previous history of syphilis, or who had more than one partner during the pregnancy were at increased risk of syphilis. While 76% of the study population had received prenatal care, only 17% had syphilis testing carried out during the pregnancy; 91% of serum samples that were reactive to rapid plasma reagin (RPR) tests were also reactive to fluorescent treponemal antibody-absorption (FTA-ABS) testing. There was 96% agreement between the results from local hospital laboratories and national reference laboratories in their testing of RPR reactivity of serum samples. Congenital syphilis infection was confirmed by laboratory tests in 15% of 66 infants born to women with positive RPR and FTA-ABS testing.

CONCLUSION

These results indicate that a congenital syphilis prevention programme in Bolivia could substantially reduce adverse infant outcomes due to this disease.

The use of Western blotting as the confirmatory test for syphilis in patients with rheumatic disease

OBJECTIVE

As a direct or indirect result of antiphospholipid antibody production, subjective laboratory interpretation, and false positive results, the common serologic tests for syphilis have been inherently inaccurate diagnostic tests in patients with systemic lupus erythematosus (SLE) and other autoimmune diseases. We assessed the diagnostic accuracy of syphilis testing in patients with SLE and other autoimmune diseases using the treponemal Western blot (TWB) as the gold standard.

METHODS

A prospective cohort study carried out at a tertiary care medical center. We studied 107 patients with autoimmune disease, 50 with at least one positive serologic test for syphilis and 57 disease matched controls. Prior to enrollment all eligible patients underwent a clinical assessment performed by at least 2 rheumatologists to confirm a diagnosis of rheumatic disease. All subjects underwent serologic testing, in blinded fashion, for syphilis using the rapid plasma reagin test (RPR), Venereal Disease Research Laboratory test (VDRL), fluorescent treponemal antibody absorption test (FTA-ABS), and the TWB.

RESULTS

Eighty-seven percent of the patients studied were female, the mean age was 46.5 years, and the most common diagnosis at the time of enrollment was SLE. Using the TWB as the gold standard diagnostic test for syphilis, the sensitivity, specificity, and positive predictive values for each syphilis test were calculated. The sensitivity and specificity for the RPR in patients with rheumatic disease was 62.5% (95% confidence interval 24.5 to 91.5%) and 91.9% (95% CI 84.2 to 96.2%), respectively. The sensitivity and specificity for the VDRL were 37.5% (95% CI 8.5 to 75.5%) and 89.9% (95% CI 81.8 to 94.8%), respectively. Confirmatory syphilis testing using the FTA-ABS showed a sensitivity of 100% (95% CI 68.6 to 100%) and a specificity of 67.7% (95% CI 57.4 to 76.5%). Eight patients tested positive for syphilis by Western blotting. For the FTA-ABS test, there was a significantly higher number of false positive results (n = 32) compared to false negative results (n = 0), p < 0.0005.

CONCLUSION

The FTA-ABS is not an accurate confirmatory test for syphilis in patients with SLE and other autoimmune diseases. While a negative FTA-ABS may exclude syphilis infection in the majority of cases, a positive FTA-ABS test result cannot assuredly confirm syphilis infection in this population. Western blotting is an accurate confirmatory test for syphilis and may be necessary to unequivocally discern the immunological response of syphilis from that of an underlying autoimmune disease.

An analysis of the value of some antigen-antibody interactions used as diagnostic indicators in a treponemal Western blot (TWB) test for syphilis

Densiometric quantitation and spreadsheet normalization were used to refine the parameters defining a treponemal Western blot (TWB) test for syphilis. Initially using 84 defined reactive and 105 defined non-reactive sera, we determined that the immune response to the 17 kDa antigen was the most critical of the following three candidate test determinants: the 47 kDa, 17 kDa and 15.5 kDa bands. In a second study using 124 cases of clinically diagnosed syphilis and 354 "normal" donors, a diluted serum sample was included as a minimal reactive control for the 17-kDa immune response. Reactivity to all three test determinants was obligatory for a test result to be interpreted as positive. Of the 124 cases of syphilis, 7 were nonreactive by TWB (sensitivity = 94%); of the 354 normal donors, 7 tested reactive (specificity = 98%). Forty (11%) normal serum samples had detectable but less than minimal reactivity to the 17 kDa band. Frequencies of immune response to a larger group of 12 antigens were tallied for the 124 clinically diagnosed cases of syphilis and an equal subset (124) of the normal group. In the normal subset, 72% and 52% of the samples had detectable reactivity to the 47 and 15.5 kDa antigens, respectively, while 10%, 5% and 3% reacted with the 17, 24 and 44.5 kDa antigens, respectively. Follow-up TWB testing of the clinically diagnosed cases revealed that previously untreated patients with primary or secondary syphilis were more likely to a show decrease in TWB reactivity than patients with latent symptoms who had been treated previously. As a diagnostic indicator of syphilis, the 17-kDa antigen was found to have the best combined attributes of sensitivity and specificity. Although, the highly specific 44.5 kDal and 24 kDal bands were often redundant as diagnostic indicators they are useful for the interpretation of borderline results. In addition, absence of the highly sensitive 47 and 15.5 kDa indicators should be useful in resolving some problem diagnoses.

Congenital syphilis in a newborn: an immunopathologic study

A 3-week-old girl presented to the emergency room with respiratory distress and generalized maculopapular rash. The newborn was hospitalized with a presumptive diagnosis of congenital syphilis, but she died after 2 days of therapy. Tissue from the gastrointestinal tract, brain, liver, spleen, and lung was studied by using direct fluorescent antibody and immunohistochemical analysis (IHC) for Treponema pallidum. The inflammatory infiltrate was characterized by using IHC against CD3, CD20, CD68, and smooth muscle actin. The diagnosis of congenital syphilis was confirmed by demonstrating spirochetes in tissues with IHC and direct fluorescent antibody examination. IHC showed abundant treponemes in the small intestine and liver and occasional spirochetes in the meninges. Bacteria were seen as intact spirochetes, granular staining, or large extracellular collections of antigen. A constant pathologic feature throughout the tissues was concentric macrophage (CD68-positive) infiltrate around vessels, giving an onion-skin appearance. IHC identified the macrophages as the prime immune response in congenital syphilis.

Pathology of the umbilical cord in congenital syphilis: analysis of 25 specimens using histochemistry and immunofluorescent antibody to Treponema pallidum

Identification of Treponema pallidum in the placenta is important for diagnosis of congenital syphilis; however, spirochetes are difficult to observe in chorionic villi. To determine the sensitivity of umbilical cord examination for T pallidum, and the association of spirochetes with cord pathology, placentas were prospectively obtained from 25 women with untreated syphilis. The most common finding using hematoxylin-eosin staining was a normal-appearing umbilical cord (48%); necrotizing funisitis was the most frequent pathological lesion (36%). Spirochetes were detected using silver and immunofluorescent staining in 89% of cords, including 92% of histologically normal and 84% of abnormal cords. Three specimens showed subamnionic aggregates of spirochetes, consistent with amniotic fluid infection. Necrotizing funisitis was strongly associated with umbilical artery infection by spirochetes (P = .008). There was a 100% correlation between results of silver and immunofluorescent staining. The umbilical cord is a sensitive site for morphological confirmation of T pallidum; it is significant for the pathologist that spirochetes may often be detected in the absence of overt tissue inflammation or necrosis.