TB main cause of chronic cough in HIV-positive Zimbabweans

Tuberculosis is the most common cause of chronic cough in HIV-positive individuals in Harare, Zimbabwe, according to a study published in the June 15^th edition of Clinical Infectious Diseases. The investigators also established that PCP pneumonia and cryptococcus were the next most common causes of chronic cough in HIV-positive patients, but that their combined prevalence was less than 3%.

The World Health Organisation recommends that patients with a chronic cough of three or more weeks’ duration should be considered for tuberculosis. Because of HIV, the number of cases of tuberculosis in southern Africa has increased massively over the past twenty years. It is also likely that other HIV-related opportunistic infections contribute to the burden of chronic cough in the region, although an increased incidence of non-infectious causes of chronic cough, including asthma and smoking-related lung disease, has been noted in recent years.

Studies into the diagnosis of respiratory disease in southern Africa have often been hampered by a lack of diagnostic facilities and have focused on hospitals and tuberculosis clinics of HIV research cohorts. Few studies have looked at respiratory illness amongst individuals attending primary care.

Investigators from Zimbabwe and the United Kingdom therefore wished to determine the spectrum of disease causing cough lasting three or more weeks amongst patients attending two primary care clinics in a suburb of the Zimbabwean capital, Harare.

A total of 544 individuals aged over 16 with a three-week history of cough were included in the investigators’ analysis. All the patients had an HIV test following counselling. Sputum specimens were obtained. Chest x-rays were also performed.

Of the 544 patients included in the investigators’ analysis, 83% were HIV-positive. HIV-positive individuals (20%) were much more likely than HIV-negative patients (5%) to report a previous history of tuberculosis (p < 0.001).

Fever was significantly more common amongst HIV-positive patients (76%) than HIV-negative individuals (61%, p = 0.006), and HIV-positive individuals were also significantly more likely to have a respiratory rate above 20 breaths per minute (p = 0.008).

Tuberculosis was diagnosed in 46% of HIV-positive patients and in 30% of HIV-negative individuals. This difference was statistically significant (p = 0.007). However, lower respiratory tract infections were significantly more common amongst HIV-negative patients (42% versus 31%, p = 0.049), and HIV-negative individuals were also significantly more likely to have asthma as the cause of their chronic cough (16% versus 3%, p < 0.001).

A total of 70% of HIV-positive patients (and 74% HIV-negative individuals) had smear-positive tuberculosis, with a further 8% of HIV-positive (and 7% of HIV-negative) individuals having culture-positive tuberculosis. Chest x-rays were abnormal in 90% of patients with tuberculosis.

Only five patients (1% of HIV-positive patients) had confirmed cryptococcal disease, and only eight cases ( 3%) of HIV-positive individuals were treated for PCP. Only one case was confirmed, the other seven patients received empirical treatment.

A fungal cause of cough was diagnosed in 2% of HIV-positive patients and in 9% HIV-negative individuals.

“The present study shows a high burden of tuberculosis, cases of which were mostly smear-positive, in patients presenting to primary health care clinics in urban Harare, and an even higher burden of underlying HIV infection”, write the investigators. The investigators believe that their findings have implications for clinical practice. They recommend that treatment for PCP should be offered to individuals with smear-negative tuberculosis. They also conclude that there is “an urgent need to increase capacity for HIV testing at the primary care level and to move towards HIV testing before rather than after the final diagnosis is made”.