Table 3.

Accuracy of plasma D-dimer threshold (3070 ng/mL) in predicting persistent infection after reimplantation in two-stage exchange arthroplasty at a minimum 1-year follow-up

Test	Infection persistence	No infection persistence	Total
Plasma D-dimer (-)	1	16	17
Plasma D-dimer (+)	9	18	27
Total	10	34	44
Accuracy = 100 x 9 + 16/1 + 9 + 16 + 18 = 57% Sensitivity = 100 x 9/1 + 9 = 90% Specificity = 100 x 16/16 + 18 = 47% Positive predictive value = 100 x 9/9 + 18 = 33% Negative predictive value = 100 x 16/16 + 1 = 94% Positive likelihood ratio = 0.9/1-0.47 = 1.7 Negative likelihood ratio = 1-0.9/0.47 = 0.2