Table 4. Screening for Gonorrhea in 10,000 Women
Gonorrhea Prevalence in Population or Risk Group
| Assumptions |
Low |
Moderate |
High |
| Prevalence of gonorrhea |
0.001 |
0.01 |
0.05 | 0.1 | 0.2 |
| Sensitivity of test |
0.95 |
0.95 | 0.95 | 0.95 | 0.95 |
| Specificity of test |
0.99 |
0.99 | 0.99 | 0.99 | 0.99 |
| Effectiveness of antibiotic treatment* |
0.97 |
0.97 | 0.97 | 0.97 | 0.97 |
| Probability of PID in untreated infection* |
0.20 |
0.20 | 0.20 | 0.20 | 0.20 |
| Probability of PID in successfully treated infection* |
0.06 |
0.06 | 0.06 | 0.06 | 0.06 |
| Results |
Low |
Moderate |
High |
| Tested for gonorrhea |
10,000 |
10,000 | 10,000 | 10,000 | 10,000 |
| Cases of gonorrhea diagnosed |
9.5 |
95 | 475 | 950 | 1,900 |
| Cases of PID expected without treatment |
2 |
20 | 100 | 200 | 400 |
| Cases of gonorrhea successfully treated |
9.2 |
92 | 461 | 922 | 1,843 |
| Cases of PID expected with treatment |
0.6 |
6 | 28 | 55 | 111 |
| Cases of untreated infections (either undetected or unsuccessfully treated) |
0.8 |
8 | 39 | 79 | 157 |
| Cases of PID expected in undetected or unsuccessfully treated infection |
0.2 |
2 | 8 | 16 | 31 |
| NNS to prevent 1 case of gonorrhea |
1,085 |
109 | 22 | 11 | 5 |
| Expected number of false-positive results per 10,000 tests |
100 |
99 | 95 | 90 | 80 |
| Cases of PID prevented by screening |
1.3 |
12 | 65 | 129 | 258 |
| NNS to prevent 1 case of PID |
7,751 |
840 | 155 | 78 | 39 |
*Assumptions based on data from Gift, 2002.86
Notes: NNS, number needed to screen; PID, pelvic inflammatory disease.
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