An assessment of the cost-effectiveness of fast tracking bacteriological specimens for mycobacteria

A virtual model, using six predetermined criteria for fast tracking tuberculosis specimens was devised to improve the cost effectiveness of the MB/BacT system. All specimens received at a central laboratory were audited for the six criteria over a 6-month period. By assuming that only those specimens fulfilling these criteria were fast tracked the theoretical cost savings could be calculated. To prevent possible delay in speciating mycobacteria, the number of criteria were expanded to nine, and a further 6 month audit carried out. In the first 6-month period, 728 specimens were tested. Had the initial hypothetical criteria excluded some of the specimens, only 351 specimens would have been tested through the fast-track system at a saving of pounds sterling 942 (dollars 1696), (52%) of the total cost, but five culture results positive for environmental mycobacteria would have been delayed. In a second 6-month survey the criteria were expanded. Using these no positive culture would have been missed but the savings would only have been 26% of the total cost. Introducing exclusion criteria for rapid testing can improve the cost effectiveness of rapid culture methods with no important loss of clinically necessary information.