CREATININE CLEARANCE ESTIMATION FROM SERUM CREATININE VALUES: EVALUATION AND COMPARISON OF FIVE PREDICTIVE FORMULAE IN NIGERIAN SICKLE CELL DISEASE PATIENTS

Abstract

INTRODUCTION
This study evaluated 5 predictive formulae for calculating creatinine clearance with a
view to determining which formula compares best with measured creatinine
clearance, obtained with a 24 hour urine collection in SCD patients and controls.

METHODS
Over a period of 7 months, 100 SCD patients (79 HbSS and 21 HBSC) and 50
controls participated in the study. A case record form was used to capture the clinical
details of patients, including the weight, age, and gender, frequency of crises,
transfusion and drug history. Sample collected included 7.0ml of venous blood for
serum creatinine, full blood count and reticulocyte count estimation. A 24-hr urine
and fresh urine samples were also collected for measurement of creatinine clearance
and dip stick proteinuria, respectively. Data collected were analysed using descriptive
and inferential statistics; a p-value < 0.05 was significant.

RESULTS
The study population had a mean age of 26.2±7.4 years and the controls 25.7±4.8
years. A mean PCV of 23.9±4.3%, 31.8±4.2% and 40.9 ± 4.7% were obtained for the
SS, SC and controls, respectively. Their mean WBC, platelet counts and reticulocyte
index were within normal reference ranges. Proteinuria was observed only in SS
patients with mean values of 0.52±1.20. The mean VOC reported, as number of
episodes in one year was 3.00±1.62 for SS and 1.67±1.24 for SC patients. Transfusion
episodes, reported as number of transfusions in 2 years, showed a mean value of
0.51± 0.71 for SS and 0.05±0.22 for SC. The mean values for the measured creatinine
xv

clearance in all patients, SS, SC, and controls were 66.80±26.37ml/minute,
66.28±27.52ml/minute, 68.76±21.95ml/minute and 97.04±17.47ml/minute,
respectively. No significant correlation was observed between haemogram,
proteinuria or transfusion episodes and measured creatinine clearance in the study
population(r values all ≤ 0.3). The Cockroft and Gault formula showed a superior
assessment of renal function in the patients as reflected by the higher
r(0.654),r2(0.428) values and lower predictive error(17.23). All the formulae
performed poorly in the controls.

CONCLUSION
The Cockcroft and Gault formula drawing from its satisfactory assessment of
renal function can substitute measured creatinine clearance as a means of monitoring
renal status in SCD patients.

CREATININE CLEARANCE ESTIMATION FROM SERUM CREATININE VALUES: EVALUATION AND COMPARISON OF FIVE PREDICTIVE FORMULAE IN NIGERIAN SICKLE CELL DISEASE PATIENTS