Diagnostic methods of active pulmonary TB

ABSTRACT

Tuberculosis is considered a major cause of morbidity and mortality worldwide. According to the WHO report 9.4 million individuals were suffering from active TB in 2009 [1]. Diagnostic methods for active pulmonary TB include clinical suspicion, tuberculin skin test, acid fast bacilli stain, cultures for maycobacterium, and in recent years NNA [nucleid acid amplification]. An ideal test for pulmonary active tuberculosis should be easily performed with rapid results, it should have high sensitivity and specificity, low cost,technically easy to operate and reproducible results in a variety of settings, have the possibility of drug-susceptibility testing and could distinguish Mycobacterium tuberculosis from other mycobacteria. Direct smear sputum microscopy is the primary method for diagnosing pulmonary tuberculosis but it lacks enough sensitivity and only about 44% of all new cases are detected by this method [2]. Culture technique is still seen as the gold standard for active TB. Although, the sensitivity and specificity of culture is high, this method is slow and time consuming and needs special laboratory equipments [3,4,5]. It not only provides the detection of various mycobacterial species but also the examination of drug sensitivity. It also provides the examination of genotype for epidemiological purposes if needed. Nucleic acid amplification tests [NAATs] can be performed in one day. But NAAT are not [fully] standardized and the diagnostic accuracy is highly heterogeneous, and need experienced personnel and expensive equipments