Continue of Table 1.

Author	Population	Sample size (M/F)	Age of patients†	KL-6 levels (U/mL)		p value	AUC	Best cut-off value (U/mL)	Sn/Sp (%)
				Median (IQR)	Mean ± SD**
Xue et al. [ 10 ]	Non-severe (mild & common) COVID-19	6(2/4)	55.00 ± 18.84	N/A	241.20 ± 207.90	< 0.01	N/A
	Severe (severe & critically severe) COVID-19	15(12/3)	57.20 ± 14.25	N/A	676.60 ± 506.70
d'Alessandro et al. [ 15 ]	Non-severe COVID-19	40(21/19)	64(58, 72)	316(210, 398)	307.48 ± 144.56	< 0.0001	N/A
	Severe COVID-19	14(12/2)	65(59, 71)	1125(495, 2034)	1226.56 ± 1267.74
d'Alessandro et al. [ 16 ]	Non-severe COVID-19	10(6/4)	64(51, 64)	293(197, 362)	283.02 ± 141.90	= 0.0118	82.4%(95% CI = 62-100; p = 0.0129)	406.5	83/89
	Severe COVID-19	12(9/3)	62(60, 68)	1021(473, 1909)	1145.52 ± 1204.23
Awano et al. [ 11 ]	Non-severe COVID-19	33(23/10)	40(33, 50)	223(166, 255)	214.10 ± 68.97	< 0.001	84%	303	76.2/86.2
	Severe COVID-19	21(15/6)	64(56, 78)	338(303, 529)	N/A

^†Age of patients is presented as years in mean ± SD or median (IQR). ^**All mean ± SD values were transformed from the median (IQR), except Xue et al.^[10]. M, male; F, female; N/A, not available or not applicable; Sn, sensitivity; Sp, specificity