Inhibition of PCR in genital and urine specimens submitted for Chlamydia trachomatis testing.
We determined the frequency of PCR inhibition in genital and urine specimens submitted for Chlamydia trachomatis testing using the internal control DNA provided with the COBAS AMPLICOR C. trachomatis test and assessed methods to remove it. Inhibition occurred in 65 of 906 (7%) cervical swabs, 23 of 51 (45%) urethral swabs, and 2 of 175 (1.1%) urine samples. Overall, inhibition was eliminated in processed specimens after storage at 4 degrees C in 77 of 90 specimens (86%), freezing at -70 degrees C in 59 of 82 specimens (72%), storage at 4 degrees C followed by either 1:100 dilution in 37 of 43 specimens (86%) or 1:10 dilution in 42 of 47 specimens (89%), and phenol-chloroform extraction in 79 of 80 specimens (99%). No positive specimens were missed due to inhibition. We conclude that PCR inhibition is rare with urine specimens and infrequent with endocervical swabs but occurs frequently with urethral swabs. The frequency of PCR inhibition may be significantly reduced by methods which can be easily incorporated into the processing of specimens.
Department of Pathology and Laboratory Medicine, Ottawa General Hospital, University of Ottawa, Ontario, Canada. btoye@ogh.on.ca
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B
Toye
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W
Woods
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M
Bobrowska
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K
Ramotar
D001331:Automation; D002584:Cervix Uteri / Q000382:microbiology; D002690:Chlamydia Infections / Q000175:diagnosis*; D002692:Chlamydia trachomatis / Q000235:genetics / Q000302:isolation & purification*; D004269:DNA, Bacterial / Q000032:analysis; D005260:Female; D005831:Genital Diseases, Female / Q000175:diagnosis*; D005832:Genital Diseases, Male / Q000175:diagnosis*; D006801:Humans; D008297:Male; D016133:Polymerase Chain Reaction; D013048:Specimen Handling; D014521:Urethra / Q000382:microbiology; D014556:Urine / Q000382:microbiology
D004269:DNA, Bacterial