Estimation of renal function changes on the basis of serum creatinine levels – potential and limitations

Česká verzia

Authors: O. Schück ¹; M. Horáčková ¹; J. Smrčková ²; V. Teplan ³; M. Štollová ³; M. Pecková ¹
Authors place of work: Interní klinika FN Motol a 2. LF UK Praha Přednosta: prof. MUDr. Milan Kvapil, CSc. ¹; Pracoviště laboratorních metod Přednosta: prof. MUDr. Antonín Jabor, CSc. ²; Klinika nefrologie Přednosta: doc. MUDr. Ondřej Viklický, CSc. Institut klinické a experimentální medicíny, Praha Ředitel: doc. MUDr. Jan Malý, CSc. ³
Published in the journal: Prakt. Lék. 2009; 89(1): 42-45
Category: Diagnostis

Summary

Introduction:
In daily practice, changes of renal function are most commonly evaluated in the basis of serum creatinine (S_Cr) concentration. In this study, we tried to investigate if and how accurately S_Cr changes can be used to evaluate changes in renal creatinine clearance (C_Cr), and glomerular filtration rate (GFR) estimated on the basis of MDRD (Modification of Diet in Renal Disease) formula and accurately measured by renal inulin clearance (C_in).

Methods:
In 32 patients suffering from chronic renal disease, with average S_Cr 202 (60–564) μmol/l, C_in was repeatedly measured and GFR was calculated on the basis of S_Cr and other parameters needed according to the MDRD formula. Relationships between a difference or S_Cr ratio found in the beginning (S_Cr)₀ and the end of the study (S_Cr)_t with appropriate values of C_in a MDRD were investigated. Regression analysis and the Bland-Altman analysis were used as a statistical tool.

Results:
A highly significant linear relationship between values of (S_Cr)₀/(S_Cr)_t and (MDRD)_t/(MDRD)₀ was found (r=0,968; p<0,000). Evaluation of changes of GFR on the basis of (S_Cr)₀/(S_Cr)_t ratio yields equivalent information as evaluation of (MDRD)_t/(MDRD)₀ ratio. A significant linear dependence between values of (S_Cr)₀/(S_Cr)_t and (C_in)_t/(C_in)₀ were found, however the value of the correlation coefficient is substantially lower (r=0,474; p<0,000). Only greater changes of Cin can be evaluated on the basis of (S_Cr)₀/(S_Cr)_t.

Conclusions:
A difference in creatinine serum concentrations (S_Kr)_t - (S_Kr)₀ allows us to evaluate deterioration or amelioration of renal function, however a quantitative change of renal function cannot be determined. The (S_Cr)_t/(S_Cr)₀ ratio enables a quantitative change of C_Cr, however such an evaluation is not easy, while the relationship between (S_Cr)_t/(S_Cr)₀ and (C_Cr)_t/(C_Cr)₀ is hyperbolic. Evaluation of the reciprocal value of (S_Cr)_t/(S_Cr)₀, i.e. (S_Cr)₀/(S_Cr)_t ratio is simpler, because the relationship between this value and both estimated and measured GFR is linear. This method enables the evaluation of renal function decrease as a percentage of initial value.

Key words:
serum creatinine, glomerular filtration rate (GFR), evaluation of GFR changes.

Zdroje

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