American Board of Family Medicine (ABFM) Practice Exam 2025 - Free ABFM Practice Questions and Study Guide

The preferred lab test for diagnosing pertussis is PCR, or polymerase chain reaction. This method is highly sensitive and specific, allowing for the detection of the genetic material of Bordetella pertussis, the bacterium that causes pertussis. PCR can confirm the diagnosis even when clinical symptoms are present for an extended period.

PCR testing is particularly beneficial because it can often provide results more quickly than culture methods, which may take several days to yield results. Additionally, the sensitivity of the PCR test makes it a strong diagnostic tool, especially during the early stages of the disease when bacterial loads are typically higher.

Other tests like blood culture are less favored due to their lower sensitivity and the longer time required to obtain results. Serology can detect antibodies but is not as reliable in the acute phase of the infection, making it less useful for recent infections. Rapid antigen tests may offer quick results, but their accuracy is variable and generally lower compared to PCR. Therefore, the choice of PCR aligns best with current guidelines for accurately diagnosing pertussis in a timely manner.