Table 4.

Plasma solute levels

Solute	Plasma Solute Level
	Control	CKD	CKD/Control
Urea N, mg/dl	15±2	83±27	6 [5 to 7]
PAG, µg/dl
Total	57±43	1335±830a	23 [14 to 40]
Free	50±33	1302±844a	26 [16 to 42]
PCS, µg/dl
Total	394±210	3065±1512a	8 [5 to 12]
Free	9±5	152±98a	18 [11 to 28]
IS, µg/dl
Total	92±41	1516±696a	16 [12 to 23]
Free	2±1	89±52a	38 [24 to 60]
HIPP, µg/dl
Total	154±120	1071±816a	7 [4 to 13]
Free	49±36	537±446a	11 [6 to 20]

Plasma total and free levels of solutes measured using chemical standards. The 95% confidence intervals for ratios are in brackets. PAG, phenylacetylglutamine; PCS, p-cresol sulfate; IS, indoxyl sulfate; HIPP, hippurate.

^aP<0.001 CKD versus control. Urea N is considered different by design.