CASE REPORT: A 5-year-old Malay boy with a history of recurrent pneumonia, presented with productive cough, fever and worsening tachypnoea. Physical examination revealed coarse crepitations, reduced breath sounds and clubbing. Biochemical investigations showed that he had respiratory type 2 failure as a result of bronchiectasis. Sweat conductivity done twice was raised supporting a diagnosis of CF. Other investigations such as bronchoscopy to look for congenital anomaly of the lung, infectious disease screening and tuberculosis, fungal and viral culture and sensitivity were negative. Further cascade screening revealed high sweat conductivity results in his siblings.
DISCUSSION: Although CF prevalence is low in Malaysia, it is nevertheless an important diagnosis to be recognised as it is associated with increased morbidity.
MATERIALS AND METHODS: A total of 103 patients from the Chest Clinic of Hospital Tengku Ampuan Rahimah with sputum smears positive for acid-fast bacilli were included in this cross-sectional study. All sputa were tested using Xpert MTB/RIF to confirm the presence of M. tuberculosis complex and detect rifampicin resistance. Sputa were also sent to a respiratory medicine institute for mycobacterial culture. Positive cultures were then submitted to a reference laboratory, where isolates identified as M. tuberculosis complex underwent drug susceptibility testing (DST).
RESULTS: A total of 58 (56.3%) patients were newly diagnosed and 45 (43.7%) patients were previously treated. Xpert MTB/RIF was able to detect rifampicin resistance with a sensitivity and specificity of 87.5% and 98.9%, respectively. Assuming that a single resistant result from Xpert MTB/RIF or any DST method was sufficient to denote resistance, a total of 8/103 patients had rifampicinresistant M. tuberculosis. All eight patients were previously treated for PTB (p<0.05). The overall prevalence of rifampicin resistance among smear-positive PTB patients was 7.8%, although it was 17.8% among the previously treated ones.
CONCLUSION: The local prevalence of rifampicin-resistant M. tuberculosis was particularly high among previously treated patients. Xpert MTB/RIF can be employed in urban district health facilities not only to diagnose PTB in smear-positive patients, but also to detect rifampicin resistance with good sensitivity and specificity.