14th Annual Conference of the British HIV Association 23–25 April 2008, Belfast

IDENTIFYING HIV INFECTION IN DIAGNOSTIC HISTOPATHOLOGY TISSUE SAMPLES

HIV Med 2008; 9(Suppl. 1):2 (abstract no. O4)

L Alarcon, U Mahadeva, M Moonim, J van der Walt and S Lucas
Dept of Histopathology, St Thomas’ Hospital, London, UK

Using immunocytochemistry, HIV-1 infection can be visualised in fixed tissue samples.

AIM: To investigate the practicalities and utilities of routine HIV-1 p24 immunocytochemistry on tissue samples received in a London histopathology laboratory.

METHODS: Over a 3 year period, 2005–7, fixed tissue samples from patients (age 2–65 years) with and without known HIV infection, including primary diagnostic biopsies, consultation referrals and autopsy material, were stained with Dako anti-HIV-1-p24 antibodies. Cases were selected that, on H&E stains, morphologically suggested HIV infection, e.g. lymphoid hyperplasia in non-lymphoid organs, atypical germinal centres in lymphoid tissue, and encephalitis.

RESULTS: Of 123 cases, 36 were HIV-1 p24+ve: 24/87 lymph node, 7/13 Waldeyer’s ring, 1/3 parotid, 1/2 anus, 2/5 lung, and 1/2 brain samples. In 10/36 cases (28%), the p24+ staining was the first indication to clinicians that the patient was HIV infected, and was reported as such. These included 6 lymph node and 3 Waldeyer’s ring and 1 parotid samples. The p24+ patients had blood viral loads, where known, from <50-151462 (median 16026) copies/mL. Of the known HIV+ve cases (45), nine were p24-ve. The p24+ was characteristically dense clustered staining within CD21+ dendritic cells or microglial cells.

CONCLUSIONS: Diagnostic histopathology can identify HIV infection directly in tissue samples when the viral load is sufficiently high. As well as confirming specific pathologies such as PGL and HIV encephalitis, p24 staining identifies patients not previously known to be HIV-infected. This technique should be applied more widely to diagnose HIV+ve patients earlier and bring them into treatment programmes.

2008-04-23
O4

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