Table 2. Biomarker reference intervals by quantile regression.
| Cohort and biomarker | 2.5th quantile (90% CI), ng/mg Cr | 50th quantile (90% CI), ng/mg Cr | 97.5th quantile (90% CI), ng/mg Cr | CI:RI ratio |
|---|---|---|---|---|
| UK KIM-1 (MSD) Caucasians, male and female (n = 107) | ||||
| Age 1–4 years | 0.08 (0.03–0.12) | 0.46 (0.38–0.57) | 2.39 (1.96–2.91) | 0.41 |
| Age 5–8 years | 0.08 (0.03–0.12) | 0.46 (0.38–0.57) | 1.84 (1.62–2.10) | 0.27 |
| Age 9–12 years | 0.08 (0.03–0.12) | 0.46 (0.38–0.57) | 1.42 (1.22–1.65) | 0.32 |
| Age 13–16 years | 0.08 (0.03–0.12) | 0.46 (0.38–0.57) | 1.10 (0.87–1.39) | 0.51 |
| UK NGAL (MSD) Caucasians, females (n = 48) | ||||
| Age 1–4 years | 8.34 (3.14–22.15) | 10.49 (8.02–13.72) | 128.84 (54.03–307.25) | 2.10 |
| Age 5–8 years | 3.84 (2.64–5.60) | 15.30 (12.78–18.32) | 143.95 (81.17–255.29) | 1.24 |
| Age 9–12 years | 1.77 (0.95–3.31) | 22.31 (16.79–29.66) | 160.83 (104.23–248.19) | 0.91 |
| Age 13–16 years | 0.82 (0.22–3.01) | 32.55 (20.41–51.90) | 179.70 (100.73–320.58) | 1.23 |
| UK NGAL (MSD) Caucasians, males (n = 58) | ||||
| Age 1–16 years | 1.33 (0–1.89) | 5.21 (4.66–6.49) | 64.59 (29.14–Inf)† | Inf |
| UK KIM-1 (Luminex) Caucasians, male and female (n = 108) | ||||
| Age 1–16 years | 0.03 (0.002–0.04) | 0.17 (0.15–0.18) | 0.63 (0.49–Inf)† | Inf |
| UK NGAL (Luminex) Caucasians, females (n = 50) | ||||
| Age 1–4 years | 1.25 (0.11–14.06) | 63.43 (38.09–83.93) | 706.72 (247.84–2015.28) | 2.51 |
| Age 5–8 years | 2.72 (0.92–8.06) | 63.43 (38.09–83.93) | 581.69 (297.53–1137.25) | 1.45 |
| Age 9–12 years | 5.95 (2.41–14.70) | 63.43 (38.09–83.93) | 478.78 (327.30–700.38) | 0.79 |
| Age 13–16 years | 13.00 (1.46–116.09) | 63.43 (38.09–83.93) | 394.08 (256.72–604.94) | 0.91 |
| UK NGAL (Luminex) Caucasians, males (n = 58) | ||||
| Age 1–4 years | 0.36 (0–0.58) | 6.30 (4.53–10.18) | 229.90 (118.14–447.38) | 1.43 |
| Age 5–8 years | 0.36 (0–0.58) | 6.30 (4.53–10.18) | 180.51 (114.13–285.51) | 0.95 |
| Age 9–12 years | 0.36 (0–0.58) | 6.30 (4.53–10.18) | 141.73 (103.94–193.27) | 0.63 |
| Age 13–16 years | 0.36 (0–0.58) | 6.30 (4.53–10.18) | 111.28 (80.96–152.95) | 0.65 |
| US KIM-1 (MSD) Caucasians, male and female (n = 73) | ||||
| Age 7–8 years | 0.014 (0.007–0.032) | 0.23 (0.19–0.29) | 0.79 (0.62–Inf)† | Inf |
| Age 9–12 years | 0.031 (0.022–0.044) | 0.23 (0.19–0.29) | 0.79 (0.62–Inf)† | Inf |
| Age 13–16 years | 0.088 (0.051–0.151) | 0.23 (0.19–0.29) | 0.79 (0.62–Inf)† | Inf |
| US KIM-1 (MSD) African–American, male and female (n = 65) | ||||
| Age 7–8 years | 0.038 (0.018–0.077) | 0.17 (0.13–0.19) | 0.42 (0.34–Inf)† | Inf |
| Age 9–12 years | 0.048 (0.035–0.066) | 0.17 (0.13–0.19) | 0.42 (0.34–Inf)† | Inf |
| Age 13–16 years | 0.067 (0.043–0.106) | 0.17 (0.13–0.19) | 0.42 (0.34–Inf)† | Inf |
| US NGAL (MSD), females (n = 55) | ||||
| Age 7–8 years | 1.30 (0–4.07) | 19.30 (12.36–30.14) | 58.26 (42.06–80.70) | 0.68 |
| Age 9–12 years | 1.30 (0–4.07) | 35.38 (28.40–44.09) | 96.95 (82.72–113.64) | 0.32 |
| Age 13–16 years | 1.30 (0–4.07) | 79.40 (49.91–126.32) | 191.21 (137.58–265.74) | 0.67 |
| US NGAL (MSD), males (n = 90) | ||||
| Age 7–8 years | 1.34 (0–1.50) | 3.10 (2.55–3.77) | 8.28 (6.34–10.81) | 0.64 |
| Age 9–12 years | 1.34 (0–1.50) | 4.23 (3.63–4.95) | 10.38 (8.83–12.20) | 0.37 |
| Age 13–16 years | 1.34 (0–1.50) | 6.42 (4.56–9.03) | 14.02 (10.67–18.42) | 0.61 |
95% RIs (2.5th and 97.5th quantiles) along with median values (50th quantile) and their 90% CIs were estimated using quantile regression methodology. RIs are reported by cohort (UK or USA), biomarker (KIM-1 or NGAL) and analytical method (MSD or Luminex). Where biomarker concentrations were significantly associated with sex or ethnicity (p < 0.05), RIs are presented by these partitions. We report quantile values for the middle age within each age group. A ratio of the 90% CI for the 97.5th quantile to the 95% RI (CI:RI ratio) is given. The US Cohort contained children aged 7–16 years only.
For RIs where there was no significant association with age, it was not possible to calculate upper limits for the CIs due to small sample size and the extreme percentile.
CI: Confidence interval; Cr: Creatinine; Inf: Infinity; MSD: Meso Scale Discovery; RI: Reference interval.