Combining cervical and anal-canal specimens for gonorrhea on a single culture plate

To reduce the cost of detecting gonorrhea, we studied the effect on diagnostic sensitivity of combining two culture specimens on the same plate of modified Thayer-Martin medium, using specimens from 7,787 women seen consecutively in the clinic. There was no significant difference (P greater than 0.05) between one cervical and one anal-canal specimen placed on separate plates (C,A) and these two specimens combined but spaced apart on a single plate (C/A), or between two cervical specimens combined but spaced apart on the same plate (C/C) and C/A. Therefore, C/C, C/A, and C,A have equivalent diagnostic sensitivities. C/A detected 5.68% more women with gonorrhea than did a single cervical culture (C) (P less than 0.001). If C/A were to replace C,A for culture specimens from women seen in venereal disease clinics and C for specimens taken and cultured outside of venereal disease, gonorrhea control programs in the United States could realize savings in excess of $2.5 million per year.