An evaluation of the diagnostic value of clinical and radiological manifestations in patients attending the addis ababa tuberculosis centre.

Our investigation is based on 1,000 consecutive patients attending the routine outpatient services of the Addis Ababa Tuberculosis Demonstration and Training Centre (ATBDTC) in Addis Ababa during the period November 1996-March 1997. By using sputum microscopy for acid-fast bacilli (AFB), chest radiography (CXR) and clinical assessment these patients had been diagnosed as having either AFB-positive pulmonary tuberculosis (PTB) (n = 139), AFB-negative PTB (n = 61) or non-tuberculosis (non-TB) (n = 800). These three diagnostic groups were subsequently re-assessed by us with regard to selected demographic and clinical parameters, including CXR, in order to identify and weight markers significantly linked to proven PTB. The sum of the individual weights provided diagnostic scores (DS); the average DS for AFB-positive patients was 653.5 +/- 174 and that for non-TB patients was 219.1 +/- 138.7. The calculated cut-off value between these two groups was 444. Ten (7.2%) AFB-positive PTB patents had a DS below the calculated cut-off, while 46 (5.8%) of the 800 non-TB cases had diagnostic scores exceeding this value. Our DS system achieved 92.8% sensitivity and 94.3% specificity, with positive and negative predictive values of 73.7% and 98.7%, respectively. When plotting the individual DS values of the 61 AFB-negative TB patients, 24 (39.3%) fell below the cut-off. It is most likely that these patients did not have PTB. We conclude that there is a need for improved and standardized diagnostic approaches for TB-suspected patients who depend upon clinical and CXR criteria for correct diagnosis. Our score system may be helpful in this context.