Module 9 Recording and reporting culture results

Learning objectives At the end of this module you will be able to: use the culture quantification scheme. describe the time-frame for reporting results. record culture identification results in the laboratory register. use the WHO form for a preliminary report of culture. report a M. tuberculosis complex culture on WHO form.

Content outline Culture semiquantitative reporting Detection of false-positive cultures The laboratory register for culture (DST) WHO report form for culture preliminary report final report

Laboratory culture (DST) register PATIENT Patient’s name /Lab serial number New/retreatment / follow-up (months) SPECIMEN Centre of origin / Local lab ID number Date collected/received / Type of specimen AFB smear Local result / culture lab result CULTURE logbook Media / date of inoculation Growth record (weekly) AFB morphology Date of report

Laboratory culture (DST) register ../.. ../..

Culture semiquantitative reporting READING REPORT No growth reported Fewer than 10 colonies Positive (no. of colonies) 10–100 colonies Positive (1+) More than 100 colonies Positive (2+) Innumerable or confluent growth Positive (3+) Contaminated

Laboratory register Note results immediately. Always check agreement between number on tube and number in laboratory register. Use a red pen for positive results. Check for clerical errors!

Interpretation of culture results: possible false-positive cultures due to cross-contamination Suspect cross-contamination when: there is only one positive culture among several samples; a culture turns positive after prolonged incubation; colony count on solid medium is low (1–5 colonies). Check whether the specimen was processed after one that was highly positive.

Preliminary report Date of receipt of specimen/Lab serial number AFB results (method) Culture semiquantitative reporting method Date of report / Signature

Laboratory culture (DST) register DST and identification register DST serial number Primary culture serial number Date culture positive Date DST inoculation DST logbook Controls /Drugs Identification tests Final results Identification Resistance profile Date of report

Laboratory culture (DST) register ../.. ../.. 11 11

WHO form – final report Reference lab numbers Microscopy results (indication of method) Culture growth results Identification of M. tuberculosis complex DST results Date of reporting Signature

WHO form – final report

Reporting time-frame Contaminated culture: as soon as it is identified M. tuberculosis: as soon as it is identified Negative (at 6 weeks for liquid culture) Negative (at 8 weeks)

Quality assurance Always check agreement between the laboratory register number and the number written on tubes/slants. Use WHO forms for reporting results. A copy of the completed final report should be retained in the laboratory for 2 years. 80% of the results are reported within 42 days. Positive cultures are reported within 48 hours of growth detection.

True and false exercise Early positive culture (less than 7 days) increases the suspicion of TB. TB colonies become clearly visible after at least 2 weeks (on solid media). A preliminary report should be made available to the clinician as soon as there is presumptive identification.

Module review: take-home messages Positive cultures should be reported to the clinician immediately, using a semiquantitative scale. The laboratory register and the report should be completed carefully. Keep in mind the possibility of a laboratory cross-contamination in selected cases.

Self-assessment Explain the schedule for reporting culture results. Why is semiquantitative reporting needed? What information should a final report include?