The use of two separate rapid antibody tests can accurately diagnose HIV infection in infants as early as four months after birth, and in a study of 67 infants with a median age of eleven months, this method diagnosed HIV infection with 95-97% accuracy, South African researchers reported last week at the 2006 Implementers Conference of the US President’s Emergency Plan for AIDS Relief in Durban, South Africa.

HIV diagnosis in infants under 18 months of age is complicated by the fact that infants retain maternal HIV antibodies for up to 18 months after birth. Conventional HIV antibody tests cannot distinguish between maternal and infant HIV antibodies, so it is necessary to carry out direct tests for HIV using DNA PCR testing, which is expensive and available only through well-equipped laboratories that can carry out viral load testing.

Most countries with high numbers of HIV-infected children have extremely limited capacity to carry out HIV DNA PCR tests, and in South Africa only 20% of the estimated 295,000 exposed infants received this test in 2005, despite a national recommendation that all HIV-exposed infants should receive this test at six weeks of age.
The study, carried out by researchers at Wits Paediatric HIV Clinic, set out to determine whether rapid HIV antibody tests, which are less sensitive to the presence of maternal HIV antibodies, could diagnose HIV infection as accurately as DNA PCR testing.

Samples from 67 infants were tested using HIV DNA PCR, ELISA testing (the conventional method of antibody testing), two rapid HIV antibody tests (First Response and Pareekshak) and an oral fluid rapid test (OraQuick).

	DNA PCR	ELISA	Rapid test 1	Rapid test 2	OraQuick
Positive	22	22	20	20	16
False negative		0	2#	2#	6*
Negative	45	24	44	43	43
False positive		21	1	2	2
Specificity	100%	53.3%	97.8%	95.5%	95.5%

# four false negative tests in three infants with clinical features suggestive of HIV disease
*six false negative tests in the presence of severe oral candida or WHO stage IV disease


Rapid tests detected seroreversion earlier than ELISA tests, and could detect seroreversion as early as 4.3 months after birth. However, Wits Paediatric HIV Clinic recommends that dual rapid testing should be carried out at nine months of age with a clinical examination.


Reference

Blackburn L et al. HIV rapid tests can be used as a screening tool to reduce HIV DNA PCR assays in a resource-poor setting. The 2006 HIV/AIDS Implementers Meeting of the President’s Emergency Plan for AIDS Relief, Durban, South Africa, abstract 402.

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