Table 1

Summary of audit data showing the number of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infections identified by cobas 4800 CT/NG PCR screen and confirmed by second specimens, and the number of patients who waited for the second specimen results before accepting antibiotic therapy

Specimen typeTested* Reported positiveReported equivocalEquivocal patients returnedReturned patients gave 2nd specimenInfection confirmed by 2nd specimenInfection not confirmed by 2nd specimenPCR screen PPV (%) PCR screen specificity (%)Prevalence in this specimen type (%)Equivocal patients treatedPatients treated after 2nd result
CT urine15 225923664535171898.1299.876.17544
CT swabs
CT total (%)16 781972 (5.75)78 (0.5)56412219 656
NG urine15 253762221198.7299.990.5021
  • * Excludes 38 and 161 samples, which gave invalid or clot error results respectively on the PCR screen; 11 and 28 of the samples were chlamydia and gonorrhoea positive, respectively, by in-house confirmation PCR or culture.

  • PPV calculations are based on confirmed positive and negative results and do not include ‘equivocal’ patients who did not submit a second sample for analysis, as their infection status could not be determined.

  • PPV, positive predictive value.