1. Module 9 Recording and reporting culture results

2. 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.

3. 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

4. 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

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

6. 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

7. 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!

8. 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.

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

10. 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

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

12. 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

13. WHO form – final report

14. 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)

15. 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.

16. 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.

17. 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.

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