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American Journal of Kidney Diseases

Estimation of GFR in South Asians: A Study From the General Population in Pakistan

Published:September 30, 2013DOI:https://doi.org/10.1053/j.ajkd.2013.07.023

      Background

      South Asians are at high risk for chronic kidney disease. However, unlike those in the United States and United Kingdom, laboratories in South Asian countries do not routinely report estimated glomerular filtration rate (eGFR) when serum creatinine is measured. The objectives of the study were to: (1) evaluate the performance of existing GFR estimating equations in South Asians, and (2) modify the existing equations or develop a new equation for use in this population.

      Study Design

      Cross-sectional population-based study.

      Setting & Participants

      581 participants 40 years or older were enrolled from 10 randomly selected communities and renal clinics in Karachi.

      Predictors

      eGFR, age, sex, serum creatinine level.

      Outcomes

      Bias (the median difference between measured GFR [mGFR] and eGFR), precision (the IQR of the difference), accuracy (P30; percentage of participants with eGFR within 30% of mGFR), and the root mean squared error reported as cross-validated estimates along with bootstrapped 95% CIs based on 1,000 replications.

      Results

      The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) creatinine equation performed better than the MDRD (Modification of Diet in Renal Disease) Study equation in terms of greater accuracy at P30 (76.1% [95% CI, 72.7%-79.5%] vs 68.0% [95% CI, 64.3%-71.7%]; P < 0.001) and improved precision (IQR, 22.6 [95% CI, 19.9-25.3] vs 28.6 [95% CI, 25.8-31.5] mL/min/1.73 m2; P < 0.001). However, both equations overestimated mGFR. Applying modification factors for slope and intercept to the CKD-EPI equation to create a CKD-EPI Pakistan equation (such that eGFRCKD-EPI(PK) = 0.686 × eGFRCKD-EPI1.059) in order to eliminate bias improved accuracy (P30, 81.6% [95% CI, 78.4%-84.8%]; P < 0.001) comparably to new estimating equations developed using creatinine level and additional variables.

      Limitations

      Lack of external validation data set and few participants with low GFR.

      Conclusions

      The CKD-EPI creatinine equation is more accurate and precise than the MDRD Study equation in estimating GFR in a South Asian population in Karachi. The CKD-EPI Pakistan equation further improves the performance of the CKD-EPI equation in South Asians and could be used for eGFR reporting.

      Index Words

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      Linked Article

      • Validating GFR Estimating Samples With Clinical Outcomes
        American Journal of Kidney DiseasesVol. 63Issue 5
        • Preview
          Jessani et al1 recently reported that the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation estimated glomerular filtration rate (GFR) more accurately than the MDRD (Modification of Diet in Renal Disease) Study equation in a Pakistani population. Because both equations overestimated measured GFR, the authors also developed a modification to the CKD-EPI equation to eliminate bias and improve accuracy. While I appreciate the study’s methodology and use of a general population in Pakistan, the lack of an external validation study is a major limitation, as the authors discussed.
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