American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

How should blood culture specimens be collected for a patient with an unexplained fever?

1. 1 blood culture every hour until 4 cultures are done

2. 3 blood cultures at once

3. 2 blood cultures at intervals of 45-60 minutes, 2 more at 24-48 hours

4. Only 1 blood culture

The correct answer is: 2 blood cultures at intervals of 45-60 minutes, 2 more at 24-48 hours

Collecting blood culture specimens is a crucial step in diagnosing infections, particularly in patients presenting with an unexplained fever. The recommended method for obtaining blood cultures involves collecting multiple samples to increase the likelihood of detecting a pathogen, especially in cases where bacteremia (the presence of bacteria in the blood) is suspected. The correct approach of collecting two blood cultures at intervals of 45-60 minutes, followed by an additional two cultures 24-48 hours later, allows for the identification of transient or intermittent bacteremia. This staggered approach enhances the sensitivity of detecting organisms that may not be present at all times in the bloodstream, as some infections can cause bacteria to circulate intermittently. Moreover, the second round of cultures after a day or two can capture organisms that may grow more slowly or that were not detectable during the initial sampling. In contrast, collecting only one blood culture would greatly reduce the chance of detecting potential pathogens since the variability of bacteria presence in the blood cannot be accounted for. Collecting three cultures at once may not provide additional diagnostic value over two spaced out samples, as it does not allow for the dynamic nature of bacterial presence over time. Additionally, the strategy of collecting one culture every hour until four cultures are completed could lead to unnecessary delays and