Diagnostic Methods

Clinical reference laboratories are able to provide diagnostic testing for Chlamydia pneumoniae infections with culture, serology, or molecular methods (refer to the chart below). Currently, there is only one commercially available system for the detection of C. pneumoniae infection. When additional or specialized testing is necessary, local or state public health laboratories may be able to either provide diagnostic support or forward specimens to CDC. Better C. pneumoniae diagnostic tests are needed, including the development of a rapid, reliable and cost-effective means to detect the pathogen at the point of care. Expertise and capacity to perform diagnostics is also more widely needed at state and local public health laboratories.

Advantages, Disadvantages, and the Availability of Select C. pneumoniae Diagnostic Methods

Method	Advantages	Disadvantages	Test Setting	Recommendations 9
Culture	Provides clinical isolates for genotyping and antimicrobial susceptibilities testing Variety of acceptable specimen types 1	Time-consuming Requires specialized expertise Low specificity, can be cross reactive Low sensitivity Must be cultivated within a eukaryotic host cell High contamination potential with multiple cell passages	Reference laboratories only; not for routine diagnostics	Highly trained technician that can properly examine and interpret specific staining 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 Need for acute and convalescent paired sera Time-consuming Undesirable and time-sensitive sampling No standardization or FDA approval Not optimal for treatment decisions No reference test for validating persistent infection	Clinical services: Sera provided to a clinical laboratory testing service 4	CF, EIA and whole-inclusion fluorescence are not endorsed 5 Micro immunofluorescence (MIF) is the serological method of choice although interpretation is subjective 6 Diagnosis of acute infection based on single IgG titers is not recommended 6
Molecular	Commercially available kits High sensitivity and specificity Rapid detection Higher throughput Greater discriminatory power Provides information in time for  treatment decision Variety of acceptable specimen types 1	Expensive Requires specialized expertise and equipment Not standardized Lack of clinical and comparative validation Limited FDA approval	Clinical services: NP, OP, or sputum provided to a clinical laboratory testing service for qPCR testing 4 CDC: Multiplex qPCR used for C. pneumoniae detection in NP, OP, sputum, tissue, or CSF 2,3 Commercial/FDA cleared multi-pathogen detection system: BioFire FilmArray® (BioMerieux, Inc.) 10 is a nested multiplex PCR in a closed “lab-in-a-pouch” format for testing NP specimen	qPCR is the preferred method for the diagnosis of an acute C. pneumoniae infection 8

¹ A large variety of specimen types can be used for testing:

• Combined nasopharyngeal (NP) and oropharyngeal (OP) swabs in viral transfer media (VTM) or universal transfer media (UTM)
• NP swab in VTM/UTM
• OP swab in VTM/UTM
• Sputum
• Tissue
• Bronchial lavage (BAL) fluid
• Bronchial washings
• Cerebrospinal fluid

² Various quality control measures in place for this assay including compliance with Clinical Laboratory Improvement Amendments standards and the use of proficiency testing through Quality Control for Molecular Diagnostics.

³ Other testing performed by the CDC (not for routine diagnostic purposes) include culture and MIF serology.

⁴ State and local departments of public health may offer these diagnostic tests for the detection of C. pneumoniae.

⁵ 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 reports of low sensitivity and specificity.

⁶ MIF is the only species-specific antibody test available that can measure isotype-specific antibody titers to all Chlamydia species simultaneously. The caveat to MIF testing is the assay is technically complex and interpretation is subjective. qPCR is the preferred method of diagnostic testing for acute C. pneumoniae infection, assuming the availability of an appropriate specimen type.

⁷ Single IgG titer results are not recommended because serum samples obtained from elderly patients and from patients with chronic obstructive pulmonary disease have had persistently high IgG titers in the absence of clinically apparent disease.

⁸ PCR has demonstrated greater utility for rapid and accurate detection of etiologies, especially in outbreak settings.

⁹ 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.

¹⁰ Use of trade names or commercial sources is for identification only and does not imply endorsement by the Centers for Disease Control and Prevention or the Department of Health and Human Services.

CF – Complement fixation, EIA - enzyme immunoassay, MIF – microimmunofluorescence, qPCR – quantitative polymerase chain reaction, NP – nasopharyngeal, OP – oropharyngeal, CSF – cerebrospinal fluid

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.