Two Cases of HIV-2 Detected Among Blood Donors in US

Delays in Identification of M tuberculosis The CDC recently reported the mycobacteriology laboratory practices of 2,862 laboratories that are enrolled in federally approved proficiency testing (PT) programs. Enrollment in these PT programs is required by the 1988 Clinical Laboratory Improvement Amendments (CLIA). Of the 2,862 laboratories, 2,179 reported performing primary culture for Mycobacterium tuberculosis (TB). Of these, 1,166 (54%) referred any AFB-positive isolates to another laboratory for identification and drug-susceptibility testing, 699 (32%) performed primary culture with identification, and 314 (14%) performed primary culture, identification, and drug susceptibility testing. Rapid laboratory testing to identify and determine drug susceptibility of M tuberculosis isolates is vital to effective diagnosis, treatment, and control of TB in the community. The CDC noted that organism identifications and drug-susceptibility determinations may be delayed for a substantial proportion of TB cases, because at least 54% of laboratories referred AFB isolates to another laboratory for complete analysis. Although solid and liquid media together are recommended for cultures of M tuberculosis, the liquid-culture method is needed to detect and isolate the organism. In addition, liquid-culture methods increase the sensitivity of culture for M tuberculosis. A 1992 CDC survey of 749 laboratories indicated that only 97 (13%) were using the recommended liquid-culture method. The exclusive use of solid-medium culture methods delays isolation of M tuberculosis by an average of 7 to 10 days. The CDC recommends that laboratories should select culture tests that provide rapid identification of M tuberculosis and drug-susceptibility test results, to enable early confirmation of the diagnosis and initiation of infection control measures and casefinding. Laboratories that perform only primary cultures should determine whether referral of the patient specimens, rather than the culture isolates, may decrease the time required for identification and drug-susceptibility testing. FROM: Centers for Disease Control and Prevention. Laboratory practices for diagnosis of tuberculosis. MMWR 1995;44(31):587-590.