Follow HIV testing guidelines to avoid false positive diagnosis

Tests to confirm an HIV antibody-positive diagnosis should always be performed to ensure that HIV is not being misdiagnosed, American investigators recommend in the February 19^th edition of AIDS.

They make this recommendation after reviewing false-positive HIV diagnoses at an HIV treatment centre over a ten year period. Most of the cases of misdiagnosis involved individuals referred by other health care providers, and some of the patients were already being treated with antiretroviral therapy.

There are moves to normalise HIV testing as part of routine health care in the US to help reduce rates of undiagnosed HIV infection and late diagnosis. Confirmatory testing of suspected positive results are essential, the investigators emphasise, to avoid misdiagnosis and unnecessary costs, distress and use of services.

The investigators, at the Comprehensive Care Center in Nashville, Tennessee, performed their review after the referral from primary care of a 38-year-old man recently diagnosed with HIV. This patient reported no significant HIV risk activities and had been tested for HIV during blood donation. His ELISA antibody test was positive, but his western blot result was negative. A detailed review of his medical records revealed that he had had two other positive ELISA results and two indeterminate western blot tests in the three weeks before his referral to the clinic. An HIV viral load test confirmed that the patient was not infected with HIV.

Prompted by this case, the doctors in Nashville performed a review of all 4450 HIV patients referred to their facility between 1997 and 2007. A total of 51 of these patients were misdiagnosed and were subsequently shown to be HIV-negative. The investigators compared the characteristics of these patients with those with confirmed HIV infection to see if there were any factors associated with misdiagnosis of HIV.

Misdiagnosed patients were of a similar age to those with confirmed HIV infection (35 and 37 years respectively), but were more likely to be female (57% vs. 24%, p < 0.001), and less likely to be African-American (18% vs. 36%, p < 0.001).

Most patients (36, 71%) were referred by other medical clinics or specialists. A total of 33 patients presented to the clinic after having HIV antibody tests, but 19 (58%) of these individuals had missing or misinterpreted confirmatory tests. Only six patients self-referred to the clinic with no records of screening tests.

The investigators do not comment on the emotional distress caused by misdiagnosis, but they do note the cost and resource implications of misdiagnosis. Four of the misdiagnosed patients referred to the clinic were already taking antiretroviral therapy and three were receiving services from AIDS service organisations.

Case reports detailing misdiagnosis of HIV have suggested that malingering or Munchausen syndrome are common factors. But the Tennessee investigators emphasise that although 27% of patients at their centre with misdiagnosed HIV had a prior psychiatric diagnosis, none were suspected of either malingering or Munchausen syndrome.

They conclude, “with the recent guidelines promoting HIV screening as part of general health maintenance, providers and HIV specialists should be aware of the potential for the misdiagnosis of HIV infection if confirmatory testing guidelines are not appropriately followed.”