Clinical characteristics of sputum smear negative pulmonary tuberculosis:The association with HIV infection

Abstract

Abstract Background:There have been a massive increase of Pulmonary Tuberculosis(PTB) that has threatened to undermine achievements that had been gained by National Tuberculosis Control programs(NTLP) in most Sub-Saharan Africa. This increase is due to widespread of infection with Human immunodeficiency virus (HIV). The diagnosis of PTB in HIV infection is made difficult in the increased presence of sputum smear negative tuberculosis. Objectives:To determine clinical and laboratory features of smear negative but culture positive PTB and the relationship of these features to HIV -1 sero-status. Methodology: Study site: The study was carried out at Muhimbili National Hospital and outpatient Tuberculosis clinics of IDC, Ilala and Mwananyamala, in Dar-es-salaam Tanzania. Study subjects: Male and female patients aged 18 to 75 years who presented with more than two weeks history of cough, but had three negative sputum smears for AFB were recruited in the study. Procedures: For patients with sputum smear negative, sputum was sent for culture. Counseling and HIV testing was done to all consenting recruited patients. A chest X-ray, mantoux test, and FBP were done to each patient. Those found to have features highly suggestive of PTB received treatment according to the NTLP guidelines. The remaining received a broad-spectrum antibiotic. Results: 467 fulfilled the inclusion criteria, 127(27.2%) had sputum culture positive for Mycobacterium tuberculosis. Of the 127sputum culture positive subjects, 66(51.9%) were correctly treated with anti-TB and 61(48.1%) were missed and did not get anti TB. Of the 286 subjects' who had sputum culture negative, 107(37.4%) were wrongly treated with anti- TB and 179(62.6%) received antibiotics. HIV perse is not a predictor of culture positive. The presence of a dry cough, a high respiratory rate, a low eosinophil count, a mixed type of anaemia and presence of a cavity were found to be predictive of smear negative but culture positive PTB Conclusion: A third of patients who are investigated for PTB and found to have sputum smear negative results have active disease when sputum culture is done. The current practiced procedures of establishing PTB diagnosis are not sensitive enough to establish the correct diagnosis of TB. They under diagnose PTB and over treat people with no PTB.