Table 4 The incidence of elevated expression of of urinary NGAL in children from CKDu endemic, emerging and non-endemic regions in Sri Lanka.

Age group	RI³⁵	Endemic		Emerging		Non-endemic
Age group	RI³⁵	N_T	NGAL > RI N (%)	N_T	NGAL > RI N (%)	N_T	NGAL > RI N (%)
Boys
10.0–12.9	3.748	4	3 (0.92)^†	0	0 (0.00)	31	14 (8.54)
13.0–13.9	2.966	55	34 (10.40)^⁑	39	7 (2.24)^†	22	16 (9.76)
14.0–14.9	3.299	46	22 (6.73)	42	20 (6.39)	18	12 (7.32)
15.0–15.9	3.278	41	11 (3.36)^⁑	51	31 (9.90)	11	8 (4.88)
16.0–17.9	4.851	4	1 (0.31)	8	5 (1.60)	4	3 (1.83)
10.0–17.9		150	71 (21.71)^†	140	63 (20.13)^†	86	53 (32.32)
Girls
10.0–12.9	3.146	1	1 (0.31)^†	0	0 (0.00)	27	10 (6.10)
13.0–13.9	2.085	45	34 (10.40)^⁑	59	13 (4.15)	17	9 (5.49)
14.0–14.9	3.128	64	34 (10.40)^†	57	27 (8.63)	15	8 (4.88)
15.0–15.9	2.984	53	19 (5.81)^⁑	52	33 (10.54)^†	15	7 (4.27)
16.0–17.9	3.496	14	6 (1.83)	5	3 (0.96)	4	3 (1.83)
10.0–17.9		177	94 (28.75)	173	76 (24.28)	78	37 (22.56)
Overall		327	165 (50.46)	313	139 (44.41)	164	90 (54.87)
Extreme elevations (NGAL > 97.5th quantile of RI)
Boys		150	4 (1.22)	140	3 (0.96)	86	0 (0)
Girls		177	5 (1.55)	173	3(0.96)	78	0 (0)
Overall		327	9 (2.73)^†	313	6 (1.92)	174	0 (0)

The reference interval and the median NGAL of each age stratum are given for each age group.
The number of children in each age stratum with urinary NGAL levels above the RI (50th quantile at 90% CI) given in the previous study³⁵, for that particular age group is given as N along with its percentage with respect to the total size of the respective study group, endemic, emerging or non-endemic. Similarly, the number of children with urinary KIM-1 levels above the 97.5th quantile of RI are given as extreme elevations. Comparison of proportions of children above the RI is expressed according to Chi-squared test and for the age strata with (N < 20), Fisher's exact test was used for comparison. ^⁑Denotes significance compared to the counterparts of same age in emerging group (p < 0.05) and ^†denotes significance compared to the counterparts of same age in non-endemic group.
RI reference intervals of biomarkers, N_T total number of children in an age stratum within the study group, NGAL: neutrophil gelatinase-associated lipocalin.

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