16.2.4  Diagnosis of TB in HIV-positive patients

Clinical examination

Pulmonary tuberculosis is the most common manifestation of tuberculosis in adults infected with HIV. Tuberculosis occurs at various stages of HIV infection, with the clinical pattern correlating with the patient’s immune status and could broadly be classified as early and late presentation. If a patient presents during the early stages of HIV-infection, the symptoms of TB are usually similar to those seen in non-HIV patients. However, if the patient comes at a late stage of HIV-infection, the presentation of TB is similar to primary TB, or it may spread to different organs. The clinical features in pulmonary TB are generally similar in HIV-infected and HIV-negative patients. However, cough and spitting of blood are reported less frequently by HIV-infected patients.

Sputum examination

Most HIV-positive pulmonary TB patients are sputum smear-positive. However, the proportion of smear-negative tests is much greater in HIV-positive than in HIV-negative TB patients, especially in the late stage of HIV.

Chest X-ray in HIV-positive patients

If the sputum smear remains negative, chest X-ray can be of additional value in diagnosis. However, the appearance of the X-ray may not be typical for TB. Diagnosis of TB in the HIV-infected patient is difficult.

Diagnosis of smear-negative TB in HIV patients

Important diagnostic methods have been developed recently by the WHO. This was necessary because HIV-positive patients were presenting with a cough of two to three weeks duration and then on investigation with sputum microscopy were found to be TB negative. However, if the symptoms and clinical state still strongly suggest TB, such patients are to be divided into the ambulatory ill (which means they could walk) and the seriously ill.

The adult patient will be classified as seriously ill if one or more of the following danger signs are present:

• Unable to walk unaided
• Respiratory rate over 30 breaths per minute
• Fever of more than 39°C
• Pulse rate of over 120 heart beats per minute.

A patient classified as seriously ill on this basis should immediately be referred to a higher level health facility. When immediate referral of this type is not possible, the following measures should be undertaken in the nearest health facility with the necessary equipment and trained staff:

Sputum microscopy: at least two sputum specimens should be taken and examined, one of which should be an early-morning sputum, produced after an overnight sleep. One positive smear will be sufficient to classify a patient as a smear-positive case if the patient is HIV-positive, or if there is strong clinical suspicion of HIV infection.

HIV testing: HIV testing should be routinely offered along with sputum examination in HIV-prevalent settings for patients presenting with cough of two to three weeks’ duration. A person with an unknown HIV status (e.g. because of unavailability of HIV test kits or refusal to be tested) can be classified as HIV-positive if there is strong clinical evidence of HIV infection.