Table 1

Diagnostic performance for detection of NG DNA using PivNG compared with the cobas CT/NG test and with reactive samples retested using Xpert CT/NG as a supplementary NAAT

Positive or negative samples by assay (n)Performance
cobas NG (+) and PivNG (+)cobas NG (+) and PivNG (−)cobas NG (-) and PivNG (+)cobas NG (−) and PivNG (−)OPA % (95% CI)PPA% (95% CI),
NPA % (95% CI)		PPV % (95% CI),
NPV % (95% CI)
All samples* 288 40 2 117 90.6 (87.5 to 93.0)87.8 (83.8 to 90.9),
98.3 (94.1 to 99.5)		99.3 (97.5 to 99.8),
74.5 (67.2 to 80.7)
 Of which Xpert NG+26900
 Xpert NG−19402
Oropharyngeal swab samples 87 27 2 38 81.2 (74.3 to 86.6)76.3 (67.7 to 83.2),
95.0 (83.5 to 98.6)		97.8 (92.2 to 99.4),
58.5 (46.3 to 69.6)
 Of which Xpert NG+7400
 Xpert NG−13272
Vaginal swab samples 62 7 0 28 92.8 (85.9 to 96.5)89.9 (80.5 to 95.0),
100 (87.9 to 100.0)		100 (94.2 to 100.0),
80.0 (64.1 to 90.0)
 Of which Xpert NG+6000
 Xpert NG−270
Male urine samples 57 2 0 25 97.6 (91.7 to 99.3)96.6 (88.5 to 99.1),
100 (86.7 to 100.0)		100 (93.7 to 100.0),
92.6 (76.6 to 97.9)
 Of which Xpert NG+5600
 Xpert NG−120
Rectal swab samples 82 4 0 26 96.4 (91.2 to 98.6)95.3 (88.6 to 98.2),
100 (87.1 to 100.0)		100 (95.5 to 100.0),
86.7 (70.3 to 94.7)
 Of which Xpert NG +7900
 Xpert NG−340

  • Main analysis (cobas NG vs PivNG) values shown in bold

  • *Some patients provided more than one sample type.

  • +, positive; −, negative; CT, Chlamydia trachomatis; NAAT, nucleic acid amplification test; NG, Neisseria gonorrhoeae; NPA, negative percent agreement; NPV, negative predicted value; OPA, overall percent agreement; Piv, pilin inversion; PPA, positive percent agreement; PPV, positive predicted value.