Evaluation of the abbott LCx assay for detection of Neisseria gonorrhoeae in endocervical swab specimens from females

Abstract

The Abbott LCx Neisseria gonorrhoeae assay (Abbott Laboratories, Abbott Park, Ill.) uses a ligase chain reaction (LCR) amplification in the LCx probe system for detection of a specific nucleotide sequence in the Opa-encoding gene of N. gonorrhoeae. We evaluated the LCx assay in a comparison with conventional culture employing modified Thayer-Martin media for the detection of N. gonorrhoeae from female endocervical specimens obtained from patients attending a sexually transmitted disease clinic. Discordantly LCR-positive and culture-negative specimens were further evaluated by testing with another LCR assay which used an N. gonorrhoeae-specific pilin probe. Specimens positive by both LCR assays were considered confirmed LCx-positive specimens. A specimen was considered to contain N. gonorrhoeae when it was either culture positive or culture negative and confirmed LCx positive. A total of 403 female endocervical specimens were evaluated. The prevalence of N. gonorrhoeae in this population was 8.7%. The sensitivity and specificity of the LCx assay were 94.3 and 99.4%, and those of culture were 77.1 and 100%, respectively. The Abbott LCx assay is a rapid, sensitive method for detection of N. gonorrhoeae in female endocervical specimens.

FIG. 1

Frequency distribution of S/CO ratios. ★, false-positive S/CO ratio; —, manufacturer’s equivocal zone.

FIG. 2

Receiver operating characteristic curves. Symbols: ▴, manufacturer’s equivocal zone; ■, proposed equivocal zone.