Table 17.2 Open in new tab Laboratory... | Oxford Academic

Table 17.2

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Laboratory tests in routine chlamydial diagnosis: detection of the organism

Test	Specimen type	Limitations of use	Limitations of interpretation
Histology/cytology: stain with Gimenez, Geimsa, modified Ziehl-Neelsen or FITC-labelled antibody	Impression smears from tissue or post-mortem tissue from avians and mammals	Easy to perform Suitable for one-off test or can be automated Does not allow for therapeutic intervention	Depends on typical morphological appearance
Immunoassays
1. ELISAs (enzyme-linked immunosorbent assay): plate-based (indirect enzyme immunoassays or IDEIAs) and solid-phase	Post-mortem tissue, oropharyngeal, cloacal and faecal specimens from avians Vaginal swabs, placental and fetal tissue from mammals Respiratory material from humans	Vary in sensitivity and specificity depending on the type of samples tested Faecal material may cause false positive or false negative results. Commercial solid-phase tests are subjective. May get cross-reactivity with other bacterial species.	Positive results should be confirmed by visualization of EBs by direct IF Intermittent shedding of chlamydiae, particularly in the carrier state, may necessitate repeat testing to exclude the infective state
2. Direct fluorescent antibody (DFA) tests: direct immunofluorescence (IF)	As for ELISA	Subjective and requires expertise in reading the tests. Only commercial tests are suitable for large numbers of specimens. Vary in sensitivity and specificity depending on types of samples tested. May get cross-reactivity with other bacterial species.	Absence of representative cellular material in the specimen invalidates a negative result Differentiation of species depends on the antibody used, i.e. LPS, genus-specific; MOMP, species-specific
Nucleic acid detection
1. Polymerase chain reaction (PCR) and real-time PCR	As for ELISA	Complex method requiring rigorous technical skill and specialist equipment. Subject to extrinsic nucleic acid contamination. Useful epidemiological tool. A positive result does not necessarily indicate a current infection. Tests vary in their sensitivity and specificity.	Possibility of contamination must be excluded. A positive result may not indicate clinical relevance. Inhibitors of PCR may be present, thus invalidating a negative result. Species-specific assays are available. Real-time PCR can be used to quantify the amount of agent present in a sample.
2. DNA microarray (including genotyping)	As for ELISA	Requires specialist equipment. Sensitivity equivalent to that of real-time PCR. Expensive for large numbers of samples.	A positive result does not necessarily indicate a current infection.
Culture	As for ELISA	Contamination problems with faecal and post-mortem material. Technique is slow, difficult and special transport conditions are required to maintain chlamydial viability. Culture of avian strains presents a hazard to personnel and strict containment measures are required. Optimal sensitivity of cultures is necessary.	The predictive value of a negative result is low unless optimal conditions for transport and culture are maintained.

Test	Specimen type	Limitations of use	Limitations of interpretation
Histology/cytology: stain with Gimenez, Geimsa, modified Ziehl-Neelsen or FITC-labelled antibody	Impression smears from tissue or post-mortem tissue from avians and mammals	Easy to perform Suitable for one-off test or can be automated Does not allow for therapeutic intervention	Depends on typical morphological appearance
Immunoassays
1. ELISAs (enzyme-linked immunosorbent assay): plate-based (indirect enzyme immunoassays or IDEIAs) and solid-phase	Post-mortem tissue, oropharyngeal, cloacal and faecal specimens from avians Vaginal swabs, placental and fetal tissue from mammals Respiratory material from humans	Vary in sensitivity and specificity depending on the type of samples tested Faecal material may cause false positive or false negative results. Commercial solid-phase tests are subjective. May get cross-reactivity with other bacterial species.	Positive results should be confirmed by visualization of EBs by direct IF Intermittent shedding of chlamydiae, particularly in the carrier state, may necessitate repeat testing to exclude the infective state
2. Direct fluorescent antibody (DFA) tests: direct immunofluorescence (IF)	As for ELISA	Subjective and requires expertise in reading the tests. Only commercial tests are suitable for large numbers of specimens. Vary in sensitivity and specificity depending on types of samples tested. May get cross-reactivity with other bacterial species.	Absence of representative cellular material in the specimen invalidates a negative result Differentiation of species depends on the antibody used, i.e. LPS, genus-specific; MOMP, species-specific
Nucleic acid detection
1. Polymerase chain reaction (PCR) and real-time PCR	As for ELISA	Complex method requiring rigorous technical skill and specialist equipment. Subject to extrinsic nucleic acid contamination. Useful epidemiological tool. A positive result does not necessarily indicate a current infection. Tests vary in their sensitivity and specificity.	Possibility of contamination must be excluded. A positive result may not indicate clinical relevance. Inhibitors of PCR may be present, thus invalidating a negative result. Species-specific assays are available. Real-time PCR can be used to quantify the amount of agent present in a sample.
2. DNA microarray (including genotyping)	As for ELISA	Requires specialist equipment. Sensitivity equivalent to that of real-time PCR. Expensive for large numbers of samples.	A positive result does not necessarily indicate a current infection.
Culture	As for ELISA	Contamination problems with faecal and post-mortem material. Technique is slow, difficult and special transport conditions are required to maintain chlamydial viability. Culture of avian strains presents a hazard to personnel and strict containment measures are required. Optimal sensitivity of cultures is necessary.	The predictive value of a negative result is low unless optimal conditions for transport and culture are maintained.