Diagnostic Methods

Clinical reference laboratories can provide diagnostic testing for Chlamydia pneumoniae infections using culture, serology, or molecular methods (see chart below). Currently, there are multiple commercially available systems for the detection of C. pneumoniae infection, including several Food and Drug Administration (FDA)-cleared tests. Real-time polymerase chain reaction (PCR) is the preferred method of diagnostic testing for acute C. pneumoniae infection, assuming the availability of an appropriate specimen type. When additional or specialized testing is necessary, local or state public health laboratories can provide either diagnostic support or forward specimens to CDC.

Advantages, disadvantages, and availability of select C. pneumoniae diagnostic methods

Advantages, disadvantages, and availability of select *C. pneumoniae* diagnostic methods
Method	Advantages	Disadvantages	Test Setting	Recommendations ⁷
Culture	Recovered isolates are ideal for genotyping and antimicrobial susceptibilities testing Variety of acceptable specimen types¹	Time-consuming (may take weeks to obtain an isolate) Requires specialized expertise Low sensitivity Must be cultivated within cultured cell line	Specialized reference laboratories only; not for routine diagnosis²	Highly trained technician Cell stocks routinely tested for Mycoplasma contamination by PCR Positive results should be confirmed by an additional test, such as PCR
Serology	Commercially available kits Quantitation possible	Lacks specificity Multiple patient visits required to collect acute and convalescent paired sera specimens (time-sensitive sampling) Time-consuming Not optimal for treatment decisions No reference test for validating persistent infection	Clinical laboratories: Sera provided to a clinical laboratory testing service for EIA testing³	CF, EIA, and whole-inclusion fluorescence are not endorsed⁴ MIF is the serological method of choice although interpretation is subjective⁵ Diagnosis of acute infection based on single IgG titers is not recommended⁵
Molecular	Commercially available kits/platforms High sensitivity and specificity Rapid detection Higher throughput Provides information in time for a treatment decision Variety of acceptable specimen types¹	Expensive Requires specialized expertise and equipment	Clinical laboratories: real-time PCR using validated laboratory-developed test or commercially available FDA cleared multi-pathogen detection systems³ CDC: Multiplex real-time PCR laboratory-developed test²	Real-time PCR is the preferred method for the diagnosis of an acute C. pneumoniae infection

¹ Acceptable specimen types vary by system.

² Culture can be performed at CDC but is not used for routine diagnostic purposes.

³ State and local departments of public health may also offer these diagnostic tests for the detection of C. pneumoniae.

⁴ CF is not recommended for diagnosis of acute C. pneumoniae infection because of cross-reactivity with other Chlamydia species and other enteric bacteria. Also, the sensitivity for detecting reinfection is low. Whole-inclusion fluorescence tests are also not species-specific and have not been widely evaluated. EIA is not a recommended diagnostic method because of low sensitivity and specificity.

⁵ MIF is the only species-specific antibody test available that can measure isotype-specific antibody titers to all Chlamydia species simultaneously. However, MIF testing is technically complex and interpretation is subjective.

Refer to Standardizing Chlamydia pneumoniae assays: Recommendations from the Centers for Disease Control and Prevention (USA) and the Laboratory Centre for Disease Control (Canada) for further recommendations.

CF – Complement fixation, EIA – enzyme immunoassay, MIF – microimmunofluorescence, PCR – polymerase chain reaction

References

Benitez AJ, Thurman KA, Diaz MH, Conklin L, Kendig NE, Winchell JM. Comparison of real-time PCR and a microimmunofluorescence serological assay for the detection of Chlamydophila pneumoniae infection in an outbreak investigation. J Clin Micro. 2012;50(1):151–3.
Kumar S, Hammerschlag MR. Acute respiratory infection due to Chlamydia pneumoniae: Current status of diagnostic methods. Clin Infect Dis.2007;44:568–76.
Dowell SF, Peeling RW, Boman J, et al. Standardizing Chlamydia pneumoniae assays: Recommendations from the Centers for Disease Control and Prevention (USA) and the Laboratory Centre for Disease Control (Canada). Clin Infect Dis. 2001;33:492–502.