Fig 4.

(A) Distribution of Amplicor CT/NG test OD₄₅₀ values, showing (i) the most-recent Amplicor CT equivocal zone, (ii) the earlier Amplicor equivocal zone, and (iii) the broad equivocal zone identified using the observations of this study. (B) Amplicor CT test OD₄₅₀ (x axis) against C. trachomatis plasmid quantity (y axis), as determined by ddPCR. OD₄₅₀ values of 0.1, 0.8, and 3.1 are indicated. ddPCR values of zero are assigned an arbitrarily low (0.001 plasmids/μl) value. Positive ddPCR with high estimates of the infectious load are infrequent when the Amplicor CT/NG OD₄₅₀ is <3.1.