Correction Formula for Creatinine Concentration with Glucose in Dialysate
Charoen Kaitwatcharachai MD*, Somthawil Kaitwatcharachai BNS**, Dullached Wiriyasombat BSc***
Affiliation : * Division of Medicine, Hat Yai Hospital, Songkhla, Thailand ** Division of Nursing, Hat Yai Hospital, Songkhla, Thailand *** Division of Clinical Pathology, Hat Yai Hospital, Songkhla, Thailand
Objective : Previous studies showed that high glucose in dialysate could interfere with creatinine measurement. This error
might produce some mistakes in peritoneal dialysis (PD) treatment. The correction of creatinine is essentially needed.
Material and Method: Creatinine powder diluted in 0.1 N HCl was used as the standard reference. Different creatinine
measurements obtained from unused dialysate solutions in various glucose concentrations were performed. Creatinine
correction was performed by Twardowski’s formula which was recommended by Nephrology Society of Thailand and by
Tam’s formula which utilized unused dialysate creatinine and glucose ratio. Comparison of the results in determination of
membrane transport characteristics was based on the criteria proposed by Twardowski et al in used dialysate solutions
derived from 17 CAPD patients with different approaches.
Results : The mean creatinine concentrations obtained from the standard creatinine solution and the above two correction
methods were different. The mean creatinine derived from Twardowski’s formula was the lowest. The correlation coefficients
between glucose and creatinine interference obtained by direct measurement and by Twardowski’s formula were high (r =
0.80-0.98) at all creatinine levels. However, the correlation between glucose and creatinine interference were significant only
at creatinine concentrations of 2.9 and 17.5 mg%. Classification of membrane transport was discordant when different
correction formulae were used.
Conclusion : Creatinine correction in dialysate was crucial. Creatinine correction with fresh dialysate creatinine and glucose
ratio might be suitable in clinical practice.
Keywords : Creatinine correction, Dialysate, Glucose, Jaffe alkaline picrate method
