Reporting of negative blood culture in Category B laboratories

08 June 2021

Medico Drug Testing

An issue regarding the reporting of negative blood cultures from Category B laboratories was referred to the Human Pathology Accreditation Advisory Committee for comments.

The key issue is the assurance that the Cat B laboratory does not issue false negatives.

It was agreed that the RCPA QAP blood culture module is not appropriate as it assesses laboratories’ ability to accurately identify isolates, not whether they can recover them in culture in the initial stage.

An internal QA program to test the Cat B lab’s ability to detect organisms in a sample of blood (such a sample exchange process being sent from the supervising GX lab) is deemed a reasonable alternative to QAP – but it must be in a real or appropriately spiked blood samples.

The parent GX lab should also monitor in real time the rate of positives arising from a given Cat B lab to detect any drop off in positivity rate noting this may not be so practical if the rate is low, for example, 1 positive bottle every 1-2 months, as it might be 4-6 months or even longer before it becomes apparent that the positivity rate has dropped off.

Should you have any questions please contact your client coordinator in the first instance.