The effect of parallel and serial testing on sensitivity, specificity and predictive values for T-SPOT.TB and TST in two comparisons.

a, two tests were combined in a ‘parallel’ way that took a positive result when either test was positive and a negative result when both negative.b, two tests were combined in a ‘serial’ way that took a positive result when both test was positive and a negative result when either negative. The two tests were performed simultaneously and the word ‘serial’ only indicated the combination fashion usually done. PPV, positive predictive value; NPV, negative predictive value.