Summary Gaydos et al. Urine nucleic acid amplification tests...Articles for review.Literature review.Sexually Transmitted Diseases Diagnostics Initiative (SDI)

Literature reviews > Articles for review > Gaydos et al. Urine nucleic acid amplification tests...

Nucleic acid amplification tests used with non-invasive specimens are highly sensitive and specific.

Urine nucleic acid amplification tests for the diagnosis of sexually transmitted infections in clinical practice.
Gaydos CA, Quinn TC.
Current Opinion in Immunology 2005;18:55-66

Summary:

Question

Can self-collected genital specimens, such as urine and vaginal swabs, be used to accurately diagnose sexually transmitted infections?

Data Extraction

This review discusses the accuracy of nucleic acid molecular amplification tests and their utility in reaching individuals at highest risk of having an STI. The organisms for which the most data exists include C. trachomatis and N. gonorrhoeae.

Main Results

The performances of several diagnostic tests for the detection of C. trachomatis and N. gonorrhoeae are shown in the table. Nucleic acid amplification tests (NAAT) are more sensitive and specific than older traditional culture and non-culture methods for the diagnosis of STI.Due to their very high sensitivity, NAAT can accurately utilize urine and other non-invasive specimens such as vaginal swabs, which can be self-administered or administered by a clinician. NAAT used with urine samples include polymerase chain reaction (PCR), transcription mediated amplification (TMA), and strand displacement amplification (SDA). The advantages of NAAT are that the same specimen can be used for the detection of multiple STI, and that four or more samples can be analyzed in one pooled test unit to lower the cost per sample tested. Positive pool results lead to re-testing all samples in the pool individually. Confirmation of positive NAAT tests should be performed when the positive predictive value of a positive test is less than 90%.When used to determine a test-of-cure, NAAT may give a positive result from cells rendered non-infective by antibiotics for up to 3 weeks after therapy. Culture is still recommended for medico-legal investigations because it is 100% specific. Direct fluorescent antibody (DFA) and enzyme immunoassay tests (EIA) can no longer be recommended.

Performance of diagnostic tests for the detection of C. trachomatis and N. gonorrhoeae in urogenital specimens

Diagnostic test, specimen type	C. trachomatis (%)		N. gonorrhoeae (%)
Diagnostic test, specimen type	Sensitivity	Specificity	Sensitivity	Specificity
Culture	70-85	100	80-95	100
Gram stain, symptomatic men	NA^a	NA	90-95	95-100
Gram stain, asymptomatic men	NA	NA	50-70	95-100
Gram stain, women	NA	NA	50-70	95-100
Direct fluorescent antibody	80-85	>99	NA	NA
Enzyme immunoassay	53-76	95	NA	NA
Probe hybridization	65-83	99	92.1-96.4	98.8-99.1
PCR, cervical	89.7	99.4	92.4	99.5
PCR, female urine	89.2	99	64.8	99.8
PCR, male urine	90.3	98.4	94.1	99.9
SDA, cervical	92.8	98.1	96.6	98-100
SDA, female urine	80.5	98.4	84.9	99.3-100
SDA, male urine	93.1	93.8	97.9	92.5-100
SDA, male urethra	NP^b	NP	98.5	91.9-100
TMA, cervical	94.2	97.8	99.2	98.7
TMA, female urine	94.7	98.9	91.3	99.3
TMA, male urine	97	99.1	97.1	99.2
TMA, male urethra	95.2	98.2	98.8	98.2

^atest not applicable

^bdata not provided

Authors' Conclusions

Nucleic acid amplification tests used with non-invasive specimens are highly sensitive and specific. The use of self-obtained specimens such as urine or vaginal swabs has expanded the venues at which individuals can seek screening for STI.

Source of funding:None given

For correspondence:Charlotte A. Gaydos, 1159 Ross, 720 Rutland Avenue, Baltimore, MD 21205.E-mail address: cgaydos@jhmi.edu

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