Identifying sputum specimens of high priority for examination by enhanced mycobacterial detection, identification, and susceptibility systems (EMDISS) to promote the rapid diagnosis of infectious pulmonary tuberculosis

Aims-To compare clinical information and sputum microscopy as methods for t he selection of samples for enhanced mycobacterial detection, identificatio n, and susceptibility systems (EMDISS) to promote the rapid diagnosis of pa tients with infectious pulmonary tuberculosis. Methods-Two thousand, two hundred and sixty four specimen request forms wer e examined for clinical details, which were then used to identify specimens likely to yield Mycobacterium tuberculosis on culture. These results were compared with the results of sputum microscopy for acid fast bacilli (AFB). Both methods were assessed against the results of culture using a combinat ion of continuous automated mycobacterial liquid culture (CAMLiC) and conve ntional solid culture. Results-Classification based on clinical details was an inefficient method of identifying high priority specimens for EMDISS. Although, when given, cl inical details were often consistent, a substantial proportion of specimens arrived with no details. This approach would result in the referral of at least 16% of the workload but lead to the detection by culture of only 46% of the M tuberculosis present within it. In contrast, microscopy for AFB de fined a much smaller number of specimens (4.8% of the total), which contain ed 90% of the M tuberculosis isolates. Conclusions-Microscopy for AFB is the most efficient method for defining sp utum specimens suitable for referral for enhanced mycobacteriological techn iques. However, it is essential that the methods used for smear preparation and microscopy are of the highest possible standard, otherwise some patien ts with infectious pulmonary tuberculosis will be denied, unnecessarily, th e benefits of important advances in mycobacteriology.