Advantages and Disadvantages of Laboratory Tests for Identification of B. pertussis
- Highest yield:
- young children
- early in illness
- prior to antibiotics
- Isolation of the organism confirms pertussis.
- Important if outbreak is suspected
- Long incubation time
- Many factors affect sensitivity:
- type and quality of specimen
- age of patient
- appropriate transport
- culture media
- culture incubation time
|Direct fluorescent antibody (DFA)|| 7-44%||18-78%|
- More rapid than culture
- Uses a direct smear
- Requires the presence of large numbers of organisms (>10.000/mL)
- Requires highly trained personnel to perform the test correctly.
- Antibiotic therapy can affect binding of DFA reagent to cell wall.
- Not recommended for diagnosis of B. pertussis.
|Nucleic acid amplification testing (NAAT) such as PCR|| ~93% ||70-90%|
- Faster turnaround time than culture
- Very sensitive (< 1 CFU/5mL sample)
- Does not require viable organism
- More expensive to perform than culture
- Cross reaction with different Bordetella species
- Measures antibody in the late phase of the illness when both NAAT and culture may be negative
- Requires acute and convalescent specimens
- Infection occurring in previously vaccinated individuals may not be detectible with serologic methods.