Which statement about laboratory diagnosis of pertussis is not true?

Which statement about laboratory diagnosis of pertussis is not true?

• A. Regan-Lowe medium is the recommended medium.
• B. DFA test results are definitive and do not need to be confirmed by culture.
• C. Calcium alginate or Dacron swabs are recommended over cotton-tipped swabs for specimen collection.
• D. Material collected from the nasopharynx is optimal for detection of the causative agent.

Answer: (B)

Direct fluorescent antibody testing for pertussis can provide rapid results, but its performance is not reliable enough to serve as a sole diagnostic basis. DFA detects Bordetella pertussis antigens in clinical specimens, but it has limited sensitivity and specificity, and interpretation can be subjective. false negatives can occur when bacterial numbers are low or the organism is not well preserved, and false positives can arise from cross-reactivity with other organisms or non-specific staining. Because of these limitations, DFA results should not be considered definitive; confirmation with culture and/or molecular methods (like PCR) is standard practice to establish a true diagnosis. For confirmation, culture on an appropriate medium remains a gold-standard approach, despite its slower turnaround, and provides definitive identification of Bordetella pertussis. The recommended specimen handling and collection factors matter: using calcium alginate or Dacron swabs improves organism recovery compared with cotton-tipped swabs, and nasopharyngeal material is the most reliable site for detecting the causative agent due to the typical colonization pattern of pertussis bacteria.

Direct fluorescent antibody testing for pertussis can provide rapid results, but its performance is not reliable enough to serve as a sole diagnostic basis. DFA detects Bordetella pertussis antigens in clinical specimens, but it has limited sensitivity and specificity, and interpretation can be subjective. false negatives can occur when bacterial numbers are low or the organism is not well preserved, and false positives can arise from cross-reactivity with other organisms or non-specific staining. Because of these limitations, DFA results should not be considered definitive; confirmation with culture and/or molecular methods (like PCR) is standard practice to establish a true diagnosis.

For confirmation, culture on an appropriate medium remains a gold-standard approach, despite its slower turnaround, and provides definitive identification of Bordetella pertussis. The recommended specimen handling and collection factors matter: using calcium alginate or Dacron swabs improves organism recovery compared with cotton-tipped swabs, and nasopharyngeal material is the most reliable site for detecting the causative agent due to the typical colonization pattern of pertussis bacteria.