Kampala — HENRY Mutabazi, a 34-year-old man was diagnosed with HIV/AIDS in 2000 but could not start on antiretroviral drugs (ARVs) before establishing whether he was eligible. He then went to a clinic for a CD4 cell count, only to find he was negative.

Ponsiano Kaleebu, the acting director of the Uganda Virus Research Institute, Entebbe, says there is no recorded scientific data of a person regressing a sero status from positive to negative. It is, therefore, possible there could have been an error in the laboratory.

While opening a workshop on Quality Assurance (QA) and Quality Control in HIV Testing at Colline Hotel in Mukono recently, Kaleebu said some health facilities do not adhere to QA procedures in HIV testing.

Dr. Raymond Byaruhanga, the executive director of AIDS Information Centre, says: "The use of quality laboratory services is to minimise unwanted variations in service delivery to provide care closest to what scientific evidence dictates."

He says in order to guarantee reliable HIV test results, procedures should be followed from specimen collection, testing and reporting of results.

Christopher Otafiire, the Bushenyi district laboratory focal person, says a lady who had been on ARVs for a year once went to him to check her CD4 cell count but it later turned out she was negative.

But can an HIV-positive test done from a credible clinic by a professional later turn negative? Dr. Byaruhanga says this occurs when procedures of quality assurance are not met.

"When you test a person, you are supposed to follow the national testing alogarithm which is the serial testing. You begin with one test that is so sensitive - Determine.

If negative, no confirmatory test is done, but if positive, a confirmatory test using Stat-pak is done," says Dr. Byaruhanga. "When positive, you report positive, if negative, you go ahead and test using Unigold which is the tie-breaker.

If positive or negative with Unigold report as indicated." He says most private clinics use only Determine because it is cheap, (costs about sh1,800), while unigold costs sh14,000.

Byaruhanga says whenever the rapid test result is reactive (preliminary positive), a confirmatory test must be performed.

"Each site must have procedures for referral of either test specimens or persons for confirmatory testing when appropriate."

He says quality control ensures the information generated by the laboratory is accurate, reliable and reproducible.

Another cause of negative, positive results according to Byaruhanga is the window period.

The window period is the time your body takes to produce HIV antibodies after being infected by the virus.

Kaleebu says during this period, you might test negative because there are no detectable antibodies in the blood as yet.

"During this window period, the individual is already infectious and may unknowingly infect other people."

He says it may take three months after exposure for the results to be 97% accurate and six months to be very certain.

Byaruhanga says quality procedures should be observed from the time a person asks to be tested to the time of getting the results.

He says HIV testing personnel should be re-trained on a regular basis to cope with new techniques and ensure QA procedures are followed.

Laboratory tests examine antibody to HIV, detect specific HIV antigen, estimate viral load, enumerate CD4 cell count, isolate causative agents of HIV-associated opportunistic infections and undertake basic research on different facets of HIV.