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Assessment of accuracy of Cockcroft-Gault and MDRD formulae in critically ill Indian patients
Mohit Kharbanda1, Arghya Majumdar, S Basu
1Departments of Critical Care and Nephrology, AMRI Hospitals, Kolkata, India.
Insights
The Cockcroft-Gault (CG) and MDRD formulae overestimate Glomerular Filtration Rate (GFR) in critically ill Indian patients, despite showing a strong correlation with measured GFR. These formulas are not reliable for this population.
Area of Science:
- Nephrology
- Critical Care Medicine
- Clinical Chemistry
Background:
- The accuracy of Cockcroft-Gault (CG) and Modification of Diet in Renal Disease (MDRD) formulae for estimating Glomerular Filtration Rate (GFR) has not been validated in critically ill Indian patients.
- Quantifying discrepancies between estimated GFR (eGFR) using CG and MDRD formulae and measured GFR via 24-hour urine creatinine clearance (CrCl) is crucial for appropriate clinical management.
Purpose of the Study:
- To evaluate the validity of CG and MDRD formulae in estimating GFR in critically ill Indian patients.
- To determine the extent of discrepancy between eGFR calculated by CG and MDRD formulae and measured GFR by 24-hour urine CrCl.
Main Methods:
- A prospective cohort study was conducted involving 50 adult patients in a mixed medical-surgical intensive care unit.
- Inclusion criteria included Intensive Therapy Unit (ITU) stay >48 hours and an indwelling urinary catheter.
- Exclusion criteria comprised age <18 years, pregnancy, dialysis, urine output <400 ml/day, and use of specific medications (ranitidine, cefoxitin, trimethoprim, diuretics). GFR was measured by 24-hour urine creatinine clearance and estimated using CG and MDRD formulae. Bland Altman plots and product moment correlation coefficients were used for analysis.
Main Results:
- The mean measured GFR by 24-hour urine CrCl was 79.76 ml/min/1.73 m².
- The mean eGFR by CG formula was 90.05 ml/min/1.73 m², and by MDRD formula was 85.92 ml/min/1.73 m².
- Both formulae showed a strong correlation with measured GFR (CG: r=0.65, P<0.0001; MDRD: r=0.70, P<0.0001), but exhibited bias and imprecision (CG bias: -4.5; MDRD bias: -6.1).
Conclusions:
- The CG and MDRD formulae demonstrate a significant correlation with measured GFR in critically ill Indian patients.
- However, these formulae are not reliable for estimating GFR in this specific population.
- Both CG and MDRD formulae tend to overestimate GFR in critically ill Indian patients, necessitating caution in their clinical application.
Background:
Cockroft-Gault (CG) and Modification of Diet in Renal Disease (MDRD) formulae have not been validated in critically ill Indian patients. We sought to quantify the discrepancy, if any, in Glomerular Filteration Rate (GFR) estimated by CG and MDRD formulae with 24 hrs urine Creatinine Clearance (Cr Cl).
Materials And Methods:
Prospective cohort study in 50 adult patients in a mixed medical-surgical intensive care unit.
Inclusion Criteria:
Intensive Therapy Unit (ITU) stay >48 hrs and indwelling urinary catheter.
Exclusion Criteria:
Age <18 years, pregnancy, dialysis, urine output <400 ml/day and patients receiving ranitidine, cefoxitin, trimethoprim or diuretics. We estimated Creatinine Clearance by CG and MDRD formula and measured GFR by 24 hrs urine creatinine clearance. Bland Altman plot was used to find the difference between the paired observations. The association between the methods was measured by the product moment correlation coefficient.
Result:
The mean GFR as calculated by Creatinine Clearance was 79.76 ml/min/1.73 m(2) [95% Confidence Interval (CI) 65.79 to 93.72], that by CG formula was 90.05 ml/min/1.73 m(2) [95% CI: 74.50 to 105.60], by MDRD was 85.92 ml/min/1.73 m(2) [95% CI: 71.25 to 100.59]. The Bias and Precision between CG and Cr Cl were -4.5 and 140.24 respectively, between MDRD and Cr Cl was -6.1 and 122.52. The Correlation coefficient of CG formula as a measure of GFR was 0.65 (P < 0.0001), that of MDRD was 0.70 (P < 0.0001).
Conclusion:
We conclude that CG and MDRD formulae have a strong correlation with measured GFR but are not a reliable measure and overestimate GFR in critically ill Indian patients.
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