Diagnosing Primary HIV Infection

Summaries for Patients are a service provided by Annals to help patients better understand the complicated and often mystifying language of modern medicine.

Summaries for Patients are presented for informational purposes only. These summaries are not a substitute for advice from your own medical provider. If you have questions about this material, or need medical advice about your own health or situation, please contact your physician.

The summary below is from the full report titled "Diagnosis of Primary HIV-1 Infection." It is in the 2 January 2001 issue of Annals of Internal Medicine (volume 134, pages 25-29). The authors are ES Daar, S Little, J Pitt, J Santangelo, P Ho, N Harawa, P Kerndt, JV Giorgi, J Bai, P Gaut, DD Richman, S Mandel, and S Nichols, for the Los Angeles County Primary HIV Infection Recruitment Network.

What is the problem and what is known about it so far?

Primary HIV infection is the symptomatic illness that can occur shortly after a person becomes infected with the virus. Symptoms include fever, fatigue, sore throat, muscle aches, joint pains, and/or rash. Since symptoms such as these are commonly caused by other infections, and since HIV antibody tests do not become positive immediately after a person becomes infected, it can be difficult for doctors to diagnose primary HIV infection.

Why did the researchers do this particular study?

To determine the usefulness of various symptoms and tests in making an accurate diagnosis of primary HIV infection.

Who was studied?

The study included 436 people with possible exposures to HIV who came to teaching hospitals in Los Angeles and San Diego, California, with symptoms that could be due to primary HIV infection.

How was the study done?

The researchers collected information about the patients' symptoms, as well as risk factors for HIV infection, and performed a variety of blood tests for HIV (HIV antibody, HIV RNA, and p24 antigen). Patients were identified as actually having primary HIV infection if the virus was detected in the bloodstream (positive HIV RNA test) while antibody was not found (negative HIV antibody test). A positive HIV RNA test with a positive antibody test would have indicated that the patient had been HIV infected for a longer period rather than having primary HIV infection. The researchers then tried to determine which combinations of symptoms and tests were most useful in telling whether a person had primary HIV infection.

What did the researchers find?

Of the 436 patients, 56 had primary HIV infection. The HIV RNA test was better than the p24 antigen test at detecting the presence of primary HIV infection but was more likely to have false-positive results. Certain symptoms (fever, muscle aches, rash, night sweats, and joint pains) were more common in people who had primary HIV infection than in those who did not. However, no particular symptom or group of symptoms was accurate enough in predicting primary HIV infection to be useful in deciding which patients should have blood tests.

What were the limitations of the study?

The patients in this study had been referred to special HIV care centers for testing, so they may have had more severe symptoms than the average patient with primary HIV infection.

What are the implications of the study?

Symptoms are not very helpful in predicting who should have further tests for primary HIV infection. Testing for HIV RNA is more sensitive than testing with p24 antigen, which can miss up to 10% of persons with primary HIV infection. However, HIV RNA tests are more likely to have false-positive results and therefore should be interpreted with caution.