Table 2.

The incidence of SSI by telephone call interview and clinician’s evaluation at different time-points

Telephone call time-point	D7	D14	D30	Combined
Total paired observations	187	156	141	484
SSI diagnosed by clinical review (gold standard)	14	11	0	25
SSI correctly detected by telephone interview	11	7	0	18
Incorrect detection of SSI by telephone interview (false positive test)	0	0	0	0
Sensitivity of phone call (95%CI)	79% (49.2–95.3)	64% (30.8–89.1)	N/A	72%(50.2–87.9)
Specificity of phone call (95%CI)	100% (97.9–100)	100% (97.5–100)	N/A	100%(99.2–100)
Positive Predictive Value (PPV)	100% (71.5–100)	100%(59–100)	N/A	100%(81.5–100)
Negative Predictive Value (NPV)	98.3%(95.1–99.6)	97.3%(93.3–99.3)	N/A	95.9%(96.9–99.4)

Key: N/A- Not applicable