Paper II — 2022 July (Supplementary) (2019 Scheme) — Q22
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Paper II
2022 July (Supplementary) (2019 Scheme) · 100 marks · 180 min
Question
If the urine sample, for bacterial culture, collected by the patient is submitted to the
laboratory the next day, is it acceptable. Discuss the correct decision and the
appropriate action to be taken.
Q221 marks
Answer
This is not acceptable — a patient-collected urine sample for bacterial culture submitted the next day (rather than promptly, ideally within 1–2 hours of collection, or refrigerated if any delay is unavoidable) has almost certainly undergone significant bacterial overgrowth at room temperature, since urine is an excellent culture medium for bacterial multiplication. This renders quantitative culture results unreliable and clinically meaningless — even organisms present initially in low, insignificant numbers (e.g., from contamination during collection) can multiply to reach the ≥10⁵ CFU/mL threshold used to define significant bacteriuria, producing a false-positive result, or the growth of unrelated/contaminating organisms.
Correct decision and action:
Reject the sample and do not process it for quantitative culture.
Document the delayed/unacceptable transport time as per laboratory protocol.
Inform the patient/requesting clinician of the reason for rejection, and provide clear instruction that the fresh, clean-catch midstream urine sample must be transported to the laboratory promptly (ideally within 1–2 hours of collection) — or, if delay is anticipated, the sample should be refrigerated at 2–8°C (which can preserve sample integrity for up to 24 hours) or collected into a container with a preservative (e.g., boric acid) specifically designed to prevent bacterial overgrowth during transport.
Request a fresh, correctly collected and promptly transported sample for accurate culture and susceptibility results.
