HIV tests used be used in antenatal units that are able to promptly determine if a woman is infected with HIV, and local protocols need to be in place to ensure that HIV test results are rapidly available, according to a US study published in the February edition of the Journal of Acquired Immune Deficiency Syndromes.
Even if a woman has not received HIV treatment and care during pregnancy, it is still possible to prevent the transmission of HIV from a mother to her baby provided that antiretroviral therapy is used during delivery and certain other interventions are used, such as a caesarian delivery. Providing an infant with prophylactic antiretroviral therapy, even when the mother did not receive anti-HIV drugs, has also been shown to effectively prevent HIV transmission.
It is only possible to initiate such action if a woman’s HIV-positive status has been determined.
Accordingly, investigators from Connecticut studied all HIV testing done during labour or post-delivery in two hospitals during 2000. An earlier study indicated that approximately 7% of women gave birth at these hospitals without first testing for HIV.
Hospital A used the standard ELISA HIV test until July 2000 when it replaced it with the rapid Single Use Diagnostic System (SUDS) test, which was used throughout by Hospital B. Although both hospitals had technicians on-call to process tests, neither had full 24 hour cover.
A total of 100 HIV tests were performed on women at Hospital A. Of these 64 were ELISA tests and 36 SUDS. At Hospital B all 56 tests were SUDS. Three quarters of the women tested had not received an HIV test earlier in their pregnancy care, 9% had not attended antenatal classes, 8% had received infrequent antenatal care, 10% had a history of illicit drug use, and 4% were diagnosed with a sexually transmitted infection during pregnancy.
None of the women were HIV-positive. One SUDS test did have a false-positive, but as the woman had received a false-positive test in a previous pregnancy no interventions were initiated and the result was quickly confirmed as a false-positive.
At Hospital A, the mean time taken from admission to hospital to the provision of HIV test results fell from 35.3 hours when ELISA tests were used to eight hours with the introduction of SUDS. The mean time at Hospital B, which used SUDS throughout, was 16.3 hours.
After SUDS was introduced at Hospital A, the proportion of women who had their HIV test results available before their membranes broke increased from 2% to 36% and the proportion of women receiving their test result before delivery increased from 8% to 64%. All but one SUDS test result was available within twelve hours of birth, compared to only 22% of ELISA tests.
Investigators noted that the interval between blood samples arriving at the laboratory for testing using SUDS and the notification of results was significantly shorter at Hospital A (mean 1.4 hours) than Hospital B (mean 11.2 hours). This meant that Hospital A was more able to provide test results prior to labour (64% versus 38%).
Initially, investigators explored the possibility that this was due to different protocols for the handling of samples during the night. The difference persisted in the time the two laboratories took to process the results when samples recieved overnight were excluded. In Hospital B, 17 of the 56 blood samples were in the laboratory for more than twelve hours before the test results were reported.
The investigators noted that for results to be available early enough for to be of the greatest benefit to prevent mother-to-baby HIV transmission, then it was essential to use the rapid SUDS test.
They note, “once the SUDS test was used in Hospital A, more than one-third of the results were reported before the rupture of the membranes and almost two-thirds before delivery. In these instances, if a result had been positive, antiretroviral prophylaxis could possibly have been started before delivery and obstetric measures might have been taken to decrease the risk of transmission.” The investigators also note that, “more importantly”, nearly all the SUDS results were back within twelve hours of delivery (the crucial time to start prophylaxis in an infant). By contrast, only 22% of ELISAs were back at this point.
Equally important, the investigators stress, are protocols to ensure the rapid processing of results in the laboratory, particularly during evenings and at weekends. Given these difficulties, the investigators suggest that point-of-care HIV testing may be appropriate. For example, the recently licensed OraQuick HIV test, which is easier to read than SUDS, could be used, and the results analysed in chemistry or haematology laboratories that are open continuously.
Further information on this website
Antenatal testing and preventing mother-to-baby transmission - overview
Forsyth BW et al. Rapid HIV testing of women in labor: too long a delay. JAIDS 35: 151 – 154, 2004.