Gill Jagbir, Malyuk Rhonda, Djurdjev Ognjenka, Levin Adeera
Division of Nephrology, UBC, Centre for Health Evaluation and Outcome Sciences, Vancouver, BC, Canada.
Nephrol Dial Transplant. 2007 Oct;22(10):2894-9. doi: 10.1093/ndt/gfm289. Epub 2007 Jun 16.
Glomerular filtration rate (GFR) is the best index of kidney function. Mathematical estimations of GFR, based on serum creatinine (SCr), are a clinically useful method to follow renal function, but have certain limitations which need to be considered. Convention supports the use of Cockcroft-Gault (CG) for the purposes of drug dosing. The impact of using the modification of diet in renal disease (MDRD) formula has not been formally evaluated with respect to drug dosing; especially in an elderly multi-ethnic population. A cross-sectional study of long-term care facility patients was conducted to demonstrate the impact of the use of different formulae in the elderly for the purposes of medication dosing.
Patients with ESRD were excluded. GFR was calculated for all subjects using the four-variable modified MDRD equation (re-expressed using isotope-dilution mass spectrometry-based creatinine values) and the CG equation (corrected for body surface area). Discordance was defined as a reclassification of one stage of chronic kidney disease (CKD) by using a different formula. Calculated GFR from each formula was used to calculate the doses of two drugs: amantadine and digoxin, to demonstrate the potential impact of the use of different formulae on the risk of drug toxicity.
A total of 180 patients were identified with a mean age of 85 years, of which 30% were Asian. Mean MDRD-GFR and CG-GFR in the same group were different (72.9 ml/min/1.73 m(2) vs 52.1 ml/min/1.73 m(2)). Only 37.2% of the patients were categorized in the same stage of CKD by both methods. When MDRD was used in place of CG to determine drug dose adjustments, we found that 20% fewer patients would have qualified for a dose reduction of amantadine, which would have translated to a higher total cumulative dose delivered.
The use of CG and MDRD provided discordant estimations in over 60% of the elderly patients. While the importance of these equations cannot be questioned, caution should be exercised in situations where they have not been prospectively validated. Therefore, their interchangeable use cannot be advocated in the dosing of medications until further prospective validations are performed.
肾小球滤过率（GFR）是肾功能的最佳指标。基于血清肌酐（SCr）的GFR数学估算方法是临床上跟踪肾功能的一种有用方法，但存在一些需要考虑的局限性。传统上支持使用Cockcroft-Gault（CG）公式进行药物剂量计算。关于药物剂量计算，尚未正式评估使用肾脏病饮食改良（MDRD）公式的影响；尤其是在老年多民族人群中。进行了一项针对长期护理机构患者的横断面研究，以证明在老年人中使用不同公式进行药物剂量计算的影响。
排除终末期肾病（ESRD）患者。使用四变量改良MDRD方程（使用基于同位素稀释质谱法的肌酐值重新表达）和CG方程（校正体表面积）计算所有受试者的GFR。不一致定义为使用不同公式对慢性肾脏病（CKD）分期进行重新分类。使用每个公式计算的GFR来计算两种药物的剂量：金刚烷胺和地高辛，以证明使用不同公式对药物毒性风险的潜在影响。
共确定了180名患者，平均年龄85岁，其中30%为亚洲人。同一组中的平均MDRD-GFR和CG-GFR不同（72.9 ml/min/1.73 m²对52.1 ml/min/1.73 m²）。两种方法仅将37.2%的患者归类为同一CKD分期。当使用MDRD代替CG来确定药物剂量调整时，我们发现符合金刚烷胺剂量减少标准的患者减少了20%，这将导致更高的总累积给药剂量。
在超过60%的老年患者中，使用CG和MDRD得出的估算结果不一致。虽然这些公式的重要性毋庸置疑，但在未经前瞻性验证的情况下应谨慎使用。因此，在进行进一步的前瞻性验证之前，不能提倡在药物剂量计算中互换使用它们。
