Table 1.

Specificity and sensitivity of the method according to Ct values and different prevalence rates of the disease.

		Sensitivity (%)				Specificity (%)				PPV (%)		NPV (%)
		Positive samples (n)		95 % CI		Negative samples (n)		95 % CI		Prevalence		Prevalence
										1%	5%	1%	5%
Total		102/110	92.7	86.2	96.8	133/136	97.8	93.7	99.5	29.8	68.9	99.9	99.6
Ct groups	<20	22/22	100	84.6	100					31.4	70.5	100	100
	20−25	22/22	100	84.6	100					31.4	70.5	100	100
	25−30	22/22	100	84.6	100					31.4	70.5	100	100
	30−35	21/22	95.5	77.2	100					30.4	69.5	100	99.8
	<20−35 (total)	87/88	98.9	93.8	100					31.2	70.2	100	100
	>35	15/22	68.2	45.1	86.1					23.8	61.9	99.7	98.3

● Sensitivity, that is the probability that a test result will be positive when the disease is present (true positive rate) was calculated for each group according to the following type: a / (a + b).

● Specificity, that is the probability that a test result will be negative when the disease is not present (true negative rate) was calculated according to the following type: d / (c + d).

● Positive predictive value, that is the probability that the disease is present when the test is positive was calculated for each group according to the following type:

PPV = Se x Prevalence / Se x Prevalence + (1-Sp) x (1-Prevalence).

● Negative predictive value, that is the probability that the disease is not present when the test is negative was calculated for each group according to the following type:

NPV = Sp x (1-Prevalence) / (1-Se) x Prevalence + Sp x (1-Prevalence).