Part III: Culture
recording and reporting of laboratory results

Tuberculosis laboratories must establish a uniform procedure for reporting culture results. If laboratory findings are to be useful, they must be communicated in ways that make sense to the different authorities: Health care workers use the findings for the diagnosis and management of tuberculosis; public health authorities use them for statistical and epidemiological purposes, while tuberculosis managers use the information to ensure that bacteriologically proven patients are receiving appropriate chemotherapy.

Culture procedures for tuberculosis bacteriology are notoriously time-consuming, often taking weeks or months to complete. For this reason, interim reports should be issued. The following schedule is recommended:

• If the cultures have been contaminated, a  report should be sent out immediately and a repeat specimen requested
• If cultures are positive and growth has  been identified as M. tuberculosis a report should be sent out immediately
• At four weeks an interim report (optional) could be sent out on all negative specimens, stating that another report will be issued in the event of the specimen becoming positive later on
• At eight weeks a final report  should be issued containing all the data previously reported so that earlier interim reports can be destroyed and only the final report retained in the patients? file

Culture reports should be qualitative (ie. positive or negative) as well as quantitative (ie. number of colonies isolated). The average number of colonies on all the bottles/tubes per specimen should be reported. The following scheme is recommended:

In high tuberculosis prevalence countries more than 85% of disease is due to M. tuberculosis and other mycobacteria rarely are responsible for clinical disease. Also, the robust decontamination techniques used favour the isolation of M. tuberculosis while killing some of the more fragile mycobacteria. A positive culture with the characteristics as described before can, therefore, fairly safely be labelled as ?tubercle bacilli? and the recommended way of reporting is as follows:

?Cultivation yielded __________ growth of mycobacteria with the characteristics of tubercle bacilli?

Model tuberculosis culture reports are presented in Annex 4.

Obviously, all the technical details of each laboratory test cannot be recorded on the reports, but they should be precisely outlined in the laboratory manual and all the results must be noted in the laboratory register. A copy of the completed final report should be retained in the laboratory. When reading cultures the following should be recorded in the laboratory register:

• Growth rate (slow / rapid)
• Number of colonies isolated
• Pigment production in the colonies (none / present and colour)
• Colony morphology (rough / smooth / shiny  / flat)
• Results of differential tests

A model laboratory register is presented in Annex 5.