Table 3.

Probability of viral clearance confirmation (two negative nasopharyngeal swabs) by time from diagnosis or symptom onset and first swab negative on RT-PCR for SARS-CoV-2 in a cohort of COVID-19 subjects diagnosed before 22 April 2020 and resident in Reggio Emilia province

Time to first negative from	N° of first negative test	N° of first negative test with retest (and %)	N° of confirmed negative test (those with a negative retest) (and %)
				First positive
10–14 days	34	30 (88.2)	14/30 (46.7)
15–19 days	134	132 (98.5)	95/132 (72.0)
20–24 days	131	124 (94.7)	99/124 (79.8)
25–29 days	196	169 (86.2)	140/169 (82.8)
30–34 days	137	75 (54.7)	67/75 (89.3)
>34 days	72	24 (33.3)	21/24 (87.5)
Symptom onset
10–14 days	9	7 (77.8)	3/7 (42.9)
15–19 days	23	23 (100.0)	11/23 (47.8)
20–24 days	88	88 (100.0)	66/88 (75.0)
25–29 days	147	137 (93.2)	106/137 (77.4)
30–34 days	158	140 (88.6)	112/140 (80.0)
>34 days	279	159 (57.0)	138/159 (86.8)