Platelet concentrates are cultured to avoid bacteremia following infusion. False positive culture results are more common than true positive.
Variables:
(1) plateletpheresis versus pool of single unit product
(2) testing for anaerobic bacteria as well as aerobic
(3) method of detection (culture versus instrument)
Concentrate selection: positive initial culture or out of range for instrument.
If the initial test is positive, then a second sample of the concentrate is cultured (non-instrumental).
Confirmatory Culture
Subculture of Instrument Bottle
Interpretation
positive
NA
true positive
negative
false positive, contamination error
false positive, instrument error
not performed or cannot be interpreted
indeterminate
where:
• If an instrument is used for initial testing, then the positive bottle should be subcultured.
• In a true positive the isolated bacteria should be the same in the different specimens
• When comparing primary and secondary cultures the species of the isolates should be compared.
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Specialty: Clinical Laboratory
