RELIABILITY OF NUCLEIC-ACID AMPLIFICATION FOR DETECTION OF MYCOBACTERIUM-TUBERCULOSIS - AN INTERNATIONAL COLLABORATIVE QUALITY-CONTROL STUDY AMONG 30 LABORATORIES

Nucleic acid amplification to detect Mycobacterium tuberculosis in cli nical specimens is increasingly used as a laboratory tool for the diag nosis of tuberculosis. However, the specificity and sensitivity of the se tests may be questioned, and no standardized reagents for quality c ontrol assessment are available, To estimate the performance of amplif ication tests for routine diagnosis, we initiated an interlaboratory s tudy involving 30 laboratories in 18 countries, We prepared blinded pa nels of 20 sputum samples containing no, 100, or 1,000 mycobacterial c ells, Each laboratory was asked to detect M. tuberculosis by their rou tine method of nucleic acid amplification, Only five laboratories corr ectly identified the presence or absence bf mycobacterial DNA in all 2 0 samples, Seven laboratories detected mycobacterial DNA in all positi ve samples, and 13 laboratories correctly reported the absence of DNA in the negative samples, Lack of specificity was more of a problem tha n lack of sensitivity, Reliability was not found to be associated with the use of any particular method, Reliable detection of M. tuberculos is in clinical samples by nucleic acid amplification techniques is pos sible, but many laboratories do not use adequate quality controls, Thi s study underlines the need for good laboratory practice and reference reagents to monitor the performance of the whole assay, including pre treatment of clinical samples.