Validation of a continuous infusion of low dose Iohexol to measure glomerular filtration rate: randomised clinical trial

Table 2 Accuracy and precision of Iohexol measurements during methods A (single Iohexol bolus) and B (CILDI)

Subject	Method A	Method B	Method A	Method B
Subject	(FeCreat; %)	(FeCreat; %)	Precision (Pearson’s r)	Precision (CV; %) [no. samples]
Healthy Volunteers
1	131.7	130.8	−1.00	2.1 [7]
2	132.9	126.0	−1.00	4.4 [4]
3	125.7	122.1	−1.00	1.8 [6]
4	123.7	118.4	−1.00	6.6 [4]
5	117.2	120.4	−0.99	1.8 [7]
6	125.8	122.9	−1.00	2.0 [6]
7	121.8	125.3	−0.99	0.5 [8]
8	133.7	120.3	−0.99	1.6 [5]
9	128.1	128.7	−0.99	3.0 [7]
10	131.5	123.0	−0.97	3.8 [6]
11	121.0	120.4	−0.99	3.2 [6]
Mean	126.6	123.6		2.8 [6]
Chronic Kidney Disease
12	120.7	118.1	−1.00	2.8 [3*]
13	129.8	127.7	−0.99	4.2 [3*]
14	132.8	132.0	−1.00	4.8 [3*]
15	133.4	132.6	−1.00	2.5 [4]
16	133.0	128.4	−1.00	2.2 [3]
17	131.4	133.1	−0.90	2.6 [3*]
Mean	130.2	128.6		3.2 [3]
All volunteers
Mean	127.9	125.5		2.9

Measurements were considered to be accurate if Fe _Creat of 110-140%, using Iohexol as the denominator. Precision in method A is measured by the correlation between the log_e Iohexol concentration and time. The measurements are deemed to be precise if: −0.99 ≤ r ≥ −1. Correlation is rounded to 2 decimal places. Precision in method B is measured by the co-efficient of variation (CV) of Iohexol concentration measurements once steady state had been achieved, and has been rounded to two significant digits. The number of samples used is in parentheses. In subjects with time to steady state >8 h, the last 3 samples were used (*). Fe _Creat = fractional excretion of Creatinine, r = Pearson’s correlation, HV = healthy volunteers, CKD = chronic kidney disease.

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