Chronic kidney disease and automatic reporting of estimated glomerular filtration rate: a position statement

Aminoglycoside Clearance is a Good Estimate of Creatinine Clearance in Intensive Care Unit Patients

The aim of this study was to determine whether creatinine clearance can be estimated as well by clearance of gentamicin/tobramycin as by routine, non-invasive estimates in the intensive care unit.

The volume of distribution and clearance values for gentamicin I tobramycin were obtained using first order kinetics and an estimate of creatinine clearance derived. Seven estimates of renal function (Cockroft-Gault, MDRD4 and MDRD6 equations, two- and 24-hour urine estimates, two equations utilising Cystatin C concentrations) were compared to the gentamicin/tobramycin clearance estimate in 100 intensive care unit patients.

The gentamicin clearance estimate was at least as reliable as other estimates. The two-hour was less reliable than the 24-hour urine estimate. The Cockroft-Gault appeared to out-perform the MDRD equation estimates. The MDRD4 was not as reliable as the MDRD6 estimate. Cystatin C estimates appeared not as reliable as the gentamicin estimate of renal function.

The gentamicin/tobramycin estimate is at least as good as other estimates and it is available sooner than most others. It should be used in all patients who are prescribed gentamicin. The two-hour urine and MDRD4 estimates should not be used in the intensive care unit.

Modified diet in renal disease method overestimates renal function in selected elderly patients

BACKGROUND

the Modification of Diet in Renal Disease (MDRD) method of renal function estimation has not been extensively assessed in elderly patients. We needed to assess which renal function estimate was most suited for drug dose estimation in our population.

METHOD

we compared MDRD with an optimised version of the Cockcroft-Gault (CG(opt)) method in a hospital population, using gentamicin clearance as a baseline.

RESULTS

MDRD overestimated gentamicin clearance by 29% (P < 0.001, n = 68), while CG(opt) underestimated by 10% (P < 0.01). Overestimation by MDRD increased with increasing age. This was 12%, 26% and 69% in age groups <65, 65-80 and >80 years respectively (P < 0.001). CG(opt) underestimated renal function by -5%, -16% and -4% respectively (P = NS). Bias and precision of renal function estimations for the three age groups were less for CG(opt) than for MDRD. Age significantly influenced MDRD overestimation in this population (P = 0.037).

CONCLUSION

MDRD overestimated renal function as age increased. While CG(opt) underestimated renal function, this was of a smaller magnitude, consistent across age, and thus better suited for dose calculation, especially in the elderly. Larger-scale studies using gold standard markers of renal function estimation are urgently needed to determine the accuracy of MDRD in elderly hospitalised patients.

Mild anaemia is associated with increased all-cause mortality in heart failure

AIM

To evaluate the association of anaemia with increased long-term morbidity and mortality in hospitalised heart failure (HF) patients.

METHODS AND RESULTS

We analysed medical records of a random sample of 1000 patients admitted to tertiary care hospitals from 1996 to 2006 with a principal diagnosis of HF. Anaemia (WHO criteria) on admission was present in 45.2% of HF patients. Multivariate analysis identified anaemia as an independent predictor of 5-year mortality with a hazard ratio (HR) of 1.44 (95%CI 1.20-1.73) compared to non-anaemic patients, and a rate ratio of 1.85 (95%CI 1.72-2.02) for unplanned all-cause readmission and 1.22 (95%CI 1.16-1.29) for HF readmission within 5 years. Compared to patients in the highest gender-specific Hb quartile, those with mild anaemia (Hb 11.3-13.0 g/dL in males, 11.0-12.4 g/dL in females) had an adjusted HR of 1.32 (95%CI 1.01-1.71) for 5-year mortality. Anaemia and chronic kidney disease were independent (additive) predictors of survival, whereas anaemia interacted with prevalent diabetes (p for interaction=0.006), such that patients with both conditions had an adjusted mortality HR of 2.18 (95%CI 1.48-3.22) compared to those with diabetes only.

CONCLUSION

Mild anaemia is common in hospitalised HF patients and is an independent predictor of 5-year all-cause mortality in HF.

Validation of the revised MDRD formula and the original Cockcroft and Gault formula for estimation of the glomerular filtration rate using Australian data

AIMS

The estimation of glomerular filtration rate (eGFR) using the MDRD (Modification of Diet in Renal Disease) formula is a recommended practice in Australia, New Zealand and other countries. Since the original development of this formula, an international process to align assays for serum creatinine has been undertaken and a revised version of the MDRD formula has been produced for these assays. Additionally, the Cockcroft and Gault (C&G) formula remains recommended for drug dosing decisions, although there are different versions of the formula using either actual weight or calculated ideal body weight. We aimed to assess these formulae using Australian data.

METHODS

We assessed the revised MDRD and the C&G formulae by comparison with radio-isotope GFR measurements using patients routinely referred for this test. The MDRD was compared to GFR corrected for body surface area and the C&G to the uncorrected GFR.

RESULTS

The MDRD was shown to have the expected scatter of over +/-30% but with median values not significantly different from isotopic GFR measurements and without a systematic deviation due to age, gender, height, weight or body mass index (BMI). The original C&G formula generally provided a good estimate of GFR, however the use of ideal body weight rather than actual body weight produced an under-estimated GFR in this population which was more prominent with increasing age and BMI.

CONCLUSIONS

The MDRD and original C&G formulae were found to be valid in an Australian setting. The C&G formula, when calculated using weight estimated from patient height, was found to underestimate GFR in some patients.

Nonalbuminuric renal impairment in type 2 diabetic patients and in the general population (national evaluation of the frequency of renal impairment cO-existing with NIDDM [NEFRON] 11)

OBJECTIVE Most diabetic patients with impaired renal function have a urinary albumin excretion rate in the normal range. In these patients, the etiology of renal impairment is unclear, and it is also unclear whether this nonalbumunuric renal impairment is unique to diabetes. RESEARCH DESIGN AND METHODS In this study, we examined the frequency and predictors of nonalbumunuric renal impairment (estimated glomerular filtration rate [eGFR] <60 ml/min per 1.73 m(2)) in a nationally representative cohort of 3,893 patients with type 2 diabetes and compared our findings with rates observed in the general population from the Australian Diabetes, Obesity and Lifestyle Study (AusDiab) survey (n = 11,247). RESULTS Of the 23.1% of individuals with type 2 diabetes who had eGFR <60 ml/min per 1.73 m(2) (95% CI 21.8-24.5%), more than half (55%) had a urinary albumin excretion rate that was persistently in the normal range. This rate of renal impairment was predictably higher than that observed in the general population (adjusted odds ratio 1.3, 95% CI 1.1-1.5, P < 0.01) but was solely due to chronic kidney disease associated with albuminuria. In contrast, renal impairment in the absence of albuminuria was less common in those with diabetes than in the general population, independent of sex, ethnicity, and duration of diabetes (0.6, 0.5-0.7, P < 0.001). CONCLUSIONS Nonalbuminuric renal impairment is not more common in those with diabetes. However, its impact may be more significant. New studies are required to address the pathogenesis, prevention, and treatment of nonalbuminuric renal disease.

Evaluation of creatinine-based formulas in dosing adjustment of cancer drugs other than carboplatin

Background. Glomerular filtration rate (GFR) is often used to determine initial dosing of renally excreted cancer drugs. GFR can be calculated using the Cockcroft-Gault (CG) or the modified diet in renal diseases (MDRD) study formulas, both of which are based on serum creatinine levels. The MDRD formula is more accurate in noncancer patients, does not require patient weight, and is reported automatically by all laboratories in British Columbia, Canada. We previously showed that the CG and MDRD formulas have similar accuracy for carboplatin dosing in patients with gynecological malignancies. We now examine dosing of all renally excreted cancer drugs in the general cancer population. Since this setting does not include routine measurement of GFR, we report the concordance of estimates of GFR derived from the CG and MDRD formulas.

Methods. Patient data were collected retrospectively at the BC Cancer Agency. The primary outcome was the proportion of patients who would have received a different initial dose due to difference in the GFR. Each patient’s dose was determined from dose adjustment tables stated in specific treatment protocols. The secondary outcome was concordance of the GFR derived from CG and MDRD, using the method of Bland and Altman. A difference of >30% was assumed to be clinically significant because this difference would usually lead to dose adjustment based on reclassification of renal function.

Results. A total of 313 patients were evaluated, with 40% male. The median age was 56 years, weight 67.5 kg, height 166 cm, and serum creatinine 74 µmol/L (0.84 mg/dL). The median GFR derived from the CG and MDRD formulas were 86.8 mL/min (mean 91 mL/min, SD ± 30 mL/min) and 87.6 mL/min (mean 88 mL/min, SD ± 26 mL/min), respectively. A total of 8.6% (27/313) of patients would have received a different dose due to difference in the GFR; of these, 67% (18/27) would have received a higher dose. A difference of >30% in GFR was found in 17.9% (56/313) of patients.

Conclusions. There is good concordance of the GFR derived from the CG and MDRD formulas for most cancer patients, with less than 10% of patients expected to receive a different initial dose of chemotherapy. The MDRD formula may be a reasonable alternative to the CG formula for dosing of cancer drugs which are renally excreted or nephrotoxic. J Oncol Pharm Practice (2010) 16: 113—119.

Comparison of drug dosing recommendations based on measured GFR and kidney function estimating equations

BACKGROUND

Kidney disease alters the pharmacokinetic disposition of many medications, requiring dosage adjustment to maintain therapeutic serum concentrations. The Cockcroft-Gault (CG) equation is used for pharmacokinetic studies and drug dosage adjustments, but the Modification of Diet in Renal Disease (MDRD) Study equation is more accurate and more often reported by clinical laboratories than the CG equation.

STUDY DESIGN

Diagnostic test study.

SETTINGS & PARTICIPANTS

Pooled data set for 5,504 participants from 6 research studies and 4 clinical populations with measured glomerular filtration rate (GFR).

INDEX TEST

Estimated kidney function using the MDRD Study and CG equations incorporating actual (CG) or ideal body weight (CG(IBW)) and standardized serum creatinine concentrations.

REFERENCE TEST

Measured GFR assessed by using iodine-125-iothalamate urinary clearance.

OUTCOME

Concordance of assigned kidney function categories designated by the Food and Drug Administration (FDA) Guidance for Industry for pharmacokinetic studies and recommended dosages of 15 medications cleared by the kidneys.

RESULTS

Concordance of kidney function estimates with measured GFR for FDA-assigned kidney function categories was 78% for the MDRD Study equation compared with 73% for the CG equation (P < 0.001) and 66% for the CG(IBW) equation (P < 0.001). Concordance between the MDRD Study equation and CG and CG(IBW) equations was 78% and 75%, respectively (P < 0.001). Concordance of kidney function estimates with measured GFR for recommended drug dosages was 88% for MDRD Study equation compared with 85% for the CG equation (P < 0.001) and 82% for the CG(IBW) equation (P < 0.001), with lower concordance when dosing recommendations for drugs included narrow GFR ranges. Concordance rates between the CG and CG(IBW) equations and MDRD Study equation were 89% and 88%, respectively (P < 0.05).

LIMITATIONS

Results based on simulation rather than pharmacokinetic studies. Outcome was drug dosage recommendations, rather than observed drug efficacy and safety.

CONCLUSIONS

The MDRD Study equation can also be used for pharmacokinetic studies and drug dosage adjustments. As more accurate GFR-estimating equations are developed, they should be used for these purposes.

Comparison of drug dosing recommendations based on measured GFR and kidney function estimating equations

BACKGROUND

Kidney disease alters the pharmacokinetic disposition of many medications, requiring dosage adjustment to maintain therapeutic serum concentrations. The Cockcroft-Gault (CG) equation is used for pharmacokinetic studies and drug dosage adjustments, but the Modification of Diet in Renal Disease (MDRD) Study equation is more accurate and more often reported by clinical laboratories than the CG equation.

STUDY DESIGN

Diagnostic test study.

SETTINGS & PARTICIPANTS

Pooled data set for 5,504 participants from 6 research studies and 4 clinical populations with measured glomerular filtration rate (GFR).

INDEX TEST

Estimated kidney function using the MDRD Study and CG equations incorporating actual (CG) or ideal body weight (CG(IBW)) and standardized serum creatinine concentrations.

REFERENCE TEST

Measured GFR assessed by using iodine-125-iothalamate urinary clearance.

OUTCOME

Concordance of assigned kidney function categories designated by the Food and Drug Administration (FDA) Guidance for Industry for pharmacokinetic studies and recommended dosages of 15 medications cleared by the kidneys.

RESULTS

Concordance of kidney function estimates with measured GFR for FDA-assigned kidney function categories was 78% for the MDRD Study equation compared with 73% for the CG equation (P < 0.001) and 66% for the CG(IBW) equation (P < 0.001). Concordance between the MDRD Study equation and CG and CG(IBW) equations was 78% and 75%, respectively (P < 0.001). Concordance of kidney function estimates with measured GFR for recommended drug dosages was 88% for MDRD Study equation compared with 85% for the CG equation (P < 0.001) and 82% for the CG(IBW) equation (P < 0.001), with lower concordance when dosing recommendations for drugs included narrow GFR ranges. Concordance rates between the CG and CG(IBW) equations and MDRD Study equation were 89% and 88%, respectively (P < 0.05).

LIMITATIONS

Results based on simulation rather than pharmacokinetic studies. Outcome was drug dosage recommendations, rather than observed drug efficacy and safety.

CONCLUSIONS

The MDRD Study equation can also be used for pharmacokinetic studies and drug dosage adjustments. As more accurate GFR-estimating equations are developed, they should be used for these purposes.

Comparison of the Mayo Clinic Quadratic Equation with the Modification of Diet in Renal Disease equation and radionuclide glomerular filtration rate in a clinical setting

BACKGROUND

Recent guidelines recommend automatic reporting of estimated glomerular filtration rate (eGFR) using the abbreviated Modification of Diet in Renal Disease (MDRD) equation with every request for plasma creatinine. The Mayo Clinic Quadratic Equation (MCQE) has been put forwards as a potentially more accurate alternative. We therefore evaluated its accuracy compared with radionuclide GFR in a clinical setting.

METHOD

Data were collected on 601 patients aged 16-85 years who had undergone radionuclide GFR, and eGFR was calculated using MCQE and MDRD. Calculations of bias, correlation coefficients and percentage estimates within 30% and 50% of radionuclide GFR were used in comparisons.

RESULTS

The MCQE had a significant positive bias in the overall population but no significant bias in individuals with normal renal function defined as measured GFR > 90 mL/min per 1.73 m(2). There was no significant difference in the performance of MCQE and MDRD eGFR in patients with measured GFR > 90 mL/min per 1.73 m(2). However, in the overall group and in subjects with radionuclide GFR < 90 mL/min per 1.73 m(2), the accuracy of MDRD eGFR with respect to the proportion of patients within 30% and 50% of radionuclide GFR was better than MCQE.

CONCLUSION

MCQE compared moderately well with radionuclide GFR, although its overall bias and accuracy were inferior when compared with the MDRD equation in a clinical setting.

Implementation of the routine reporting of eGFR in Australia and New Zealand

The reporting of an eGFR (estimated glomerular filtration rate) with every requested serum creatinine concentration measurement has been successfully introduced as routine practice in Australia and New Zealand. This change in laboratory practice has been linked with a major educational initiative in the diagnosis and management of chronic kidney disease as well as standardization of a range of laboratory measurement and reporting issues. The process has been collaborative between renal physicians, chemical pathologists and laboratory scientists and their respective professional bodies, and the relevant decisions have been made collectively on the best available evidence. The initial guidelines were released in August 2005 and these have been followed up in 2007 with further recommendations to address issues arising since that time.

Recognition and management of chronic kidney disease in an elderly ambulatory population

BACKGROUND

Chronic kidney disease (CKD) is a growing problem among the elderly. Early detection is considered essential to ensure proper treatment and to avoid drug toxicity, but detection is challenging because elderly patients with CKD often have normal serum creatinine levels. We hypothesized that most cases of CKD in the elderly would go undetected, resulting in inappropriate prescribing.

OBJECTIVE

To determine whether recognition of CKD is associated with more appropriate treatment

DESIGN

Retrospective chart review

PARTICIPANTS

All patients aged >/=65 years with a measured serum creatinine in the past 3 years at 2 inner city academic health centers.

MEASUREMENTS

Estimated glomerular filtration rate (eGFR) calculated using the Modified Diet in Renal Disease equation, and for patients with eGFR < 60, documentation of CKD by the provider, diagnostic testing, nephrology referral and prescription of appropriate or contraindicated medications.

RESULTS

Of 814 patients with sufficient information to estimate eGFR, 192 (33%) had moderate (eGFR < 60 mL/min) and 5% had severe (eGFR < 30 mL/min) CKD. Providers identified 38% of moderate and 87% of severe CKD. Compared to patients without recognized CKD, recognized patients were more likely to receive an ACE/ARB (80% vs 61%, p = .001), a nephrology referral (58% vs 2%, p < .0001), or urine testing (75% vs 47%, p < .0001), and less likely to receive contraindicated medications (26% vs 40%, p = .013).

CONCLUSIONS

Physicians frequently fail to diagnose CKD in the elderly, leading to inappropriate treatment. Efforts should focus on helping physicians better identify patients with low GFR.

The impact of automated eGFR reporting and education on nephrology service referrals

Background. Serum creatinine concentration is an unreliable and insensitive marker of chronic kidney disease (CKD). To improve CKD detection, the Australasian Creatinine Consensus Working Committee recommended reporting of estimated glomerular filtration rate (eGFR) using the four-variable Modification of Diet in Renal Disease (MDRD) formula with every request for serum creatinine concentration. The aim of this study was to evaluate the impact of automated laboratory reporting of eGFR on the quantity and quality of referrals to nephrology services in Southeast Queensland, Australia.

Methods. Outpatient referrals to a tertiary and regional renal service, and a single private practice were prospectively audited over 3–12 months prior to and 12 months following the introduction of automated eGFR reporting and concomitant clinician education. The appropriateness of referrals to a nephrologist was assessed according to the Kidney Check Australia Taskforce (KCAT) criteria. Significant changes in the quantity and/or quality of referrals over time were analysed by exponentially weighed moving average (EWMA) charts with control limits based on ±3 standard deviations.

Results. A total of 1019 patients were referred to the centres during the study period. Monthly referrals overall increased by 40% following the introduction of eGFR reporting, and this was most marked for the tertiary renal service (52% above baseline). The appropriateness of nephrologist referrals, as adjudicated by the KCAT criteria, fell significantly from 74.3% in the 3 months pre-eGFR reporting to 65.2% in the 12 months thereafter (P < 0.05). Nevertheless, a greater absolute number of CKD patients were appropriately being referred for nephrologist review in the post-eGFR period (24 versus 15 per month). Patients referred following the introduction of eGFR were significantly more likely to be older (median 63.2 versus 59.3 years, P < 0.05), diabetic (25 versus 18%, P = 0.05) and have stage 3 CKD (48% versus 36%, P < 0.01).

Conclusion. The introduction of automated eGFR calculation has led to an overall increase in referrals with a small but significant decrease in referral quality. The increase in referrals was seen predominantly in older and diabetic patients with stage 3 CKD and appeared to result in net benefit.

Serial measurements of cystatin C are more accurate than creatinine-based methods in detecting declining renal function in type 1 diabetes

OBJECTIVE

Cystatin C-and creatinine-based methods were compared with (99m)-technetium-diethylene-triamine-penta-acetic acid ((99m)Tc-DTPA) plasma clearance (isotopic glomerular filtration rate [iGFR]) for detecting declining renal function.

RESEARCH DESIGN AND METHODS

Glomerular filtration rate (GFR) was monitored over a mean of 10.1 years in 85 subjects with type 1 diabetes (with an average of 5.6 measurements per individual). Baseline mean +/- SD iGFR of the cohort was 106.1 +/- 2.6 ml/min per 1.73 m(2). The rates of decline in GFR (DeltaGFR) were derived using linear regression.

RESULTS

In 19 of 85 subjects with declining renal function (i.e., DeltaiGFR >3.3 ml/min per 1.73 m(2) per year), DeltaGFR (ml/min per 1.73 m(2) per year) was 6.5 by iGFR, 4.2 by 10(4)/creatinine, 3.6 by Cockcroft-Gault formula, 3.4 by the Modification of Diet in Renal Disease (MDRD)-6 equation, and 3.5 by the MDRD-4 variable equation (P < 0.01 vs. iGFR). In comparison, DeltaGFR was 6.1 using the formula Cys-GFR = (86.7/cystatin C concentration) - 4.2 (not significant).

CONCLUSIONS

Cystatin C was more accurate in detecting decline in renal function than creatinine-based methods in this population of subjects with type 1 diabetes and a normal mean baseline GFR.

Vascular events in healthy older women receiving calcium supplementation: randomised controlled trial

OBJECTIVE

To determine the effect of calcium supplementation on myocardial infarction, stroke, and sudden death in healthy postmenopausal women.

DESIGN

Randomised, placebo controlled trial.

SETTING

Academic medical centre in an urban setting in New Zealand.

PARTICIPANTS

1471 postmenopausal women (mean age 74): 732 were randomised to calcium supplementation and 739 to placebo.

MAIN OUTCOME MEASURES

Adverse cardiovascular events over five years: death, sudden death, myocardial infarction, angina, other chest pain, stroke, transient ischaemic attack, and a composite end point of myocardial infarction, stroke, or sudden death.

RESULTS

Myocardial infarction was more commonly reported in the calcium group than in the placebo group (45 events in 31 women v 19 events in 14 women, P=0.01). The composite end point of myocardial infarction, stroke, or sudden death was also more common in the calcium group (101 events in 69 women v 54 events in 42 women, P=0.008). After adjudication myocardial infarction remained more common in the calcium group (24 events in 21 women v 10 events in 10 women, relative risk 2.12, 95% confidence interval 1.01 to 4.47). For the composite end point 61 events were verified in 51 women in the calcium group and 36 events in 35 women in the placebo group (relative risk 1.47, 0.97 to 2.23). When unreported events were added from the national database of hospital admissions in New Zealand the relative risk of myocardial infarction was 1.49 (0.86 to 2.57) and that of the composite end point was 1.21 (0.84 to 1.74). The respective rate ratios were 1.67 (95% confidence intervals 0.98 to 2.87) and 1.43 (1.01 to 2.04); event rates: placebo 16.3/1000 person years, calcium 23.3/1000 person years. For stroke (including unreported events) the relative risk was 1.37 (0.83 to 2.28) and the rate ratio was 1.45 (0.88 to 2.49).

CONCLUSION

Calcium supplementation in healthy postmenopausal women is associated with upward trends in cardiovascular event rates. This potentially detrimental effect should be balanced against the likely benefits of calcium on bone.

TRIAL REGISTRATION

Australian Clinical Trials Registry ACTRN 012605000242628.

HPLC-detected albuminuria predicts mortality

Albuminuria is a risk factor for all-cause mortality. Urinary albumin is traditionally measured with an immunochemical method such as immunonephelometry (IN). High-performance liquid chromatography (HPLC) detects additional albumin that is missed by IN, but it is unknown if HPLC-detected albuminuria also predicts mortality in the general population. We measured urinary albumin at baseline with both IN and HPLC in 10,175 participants in the longitudinal Australian Diabetes, Obesity, and Lifestyle (AusDiab) study. Over 5.2 yr of follow-up, 319 participants died. In a Cox proportional hazards regression model, participants with albuminuria measured by IN or HPLC were approximately twice as likely to die as participants who were normoalbuminuric on both assays. Receiver-operator characteristic curve analyses suggest that each test has a similar ability to predict mortality. However, the HPLC assay provided information on mortality risk that the IN assay did not capture. We conclude that albuminuria, detected by either IN or HPLC, independently predicts mortality in a community-based sample. HPLC identifies some people at increased risk of mortality that IN would not detect.

Failure to weigh patients in hospital: a medication safety risk

Often patients are not weighed in hospital. Failure to weigh patients prescribed renally excreted drugs may correlate to adverse drug events. We carried out a cross-sectional study of patients prescribed common renally excreted drugs (heparin, enoxaparin and gentamicin), admitted to two wards at Royal North Shore Hospital, Sydney over 3 months. Of all patients surveyed, 28% (22/78) in the orthopaedic ward and 22% (27/124) in the medical ward were weighed. Among those prescribed therapeutic doses of the study drugs, 25% (3/12) in the orthopaedic ward and 27% (7/26) in the medical ward were weighed. Patients prescribed therapeutic anticoagulation who were not weighed experienced more haemorrhagic complications than patients who were weighed (P = 0.03). Patients prescribed renally excreted drugs in hospital are frequently not weighed. This is associated with reduced medication safety.

Clinical pharmacology in the geriatric patient

Geriatric patients are a subset of older people with multiple comorbidities that usually have significant functional implications. Geriatric patients have impaired homeostasis and wide inter-individual variability. Comprehensive geriatric assessment captures the complexity of the problems that characterize frail older patients and can be used to guide management, including prescribing. Prescribing for geriatric patients requires an understanding of the efficacy of the medication in frail older people, assessment of the risk of adverse drug events, discussion of the harm:benefit ratio with the patient, a decision about the dose regime and careful monitoring of the patient's response. This requires evaluation of evidence from clinical trials, application of the evidence to frail older people through an understanding of changes in pharmacokinetics and pharmacodynamics, and attention to medication management issues. Given that most disease occurs in older people, and that older people are the major recipients of drug therapy in the Western world, increased research and a better evidence base is essential to guide clinicians who manage geriatric patients.

Renal insufficiency in elderly cancer patients: International Society of Geriatric Oncology clinical practice recommendations

BACKGROUND

Elderly cancer patients commonly have renal function decline. This warrants particular caution during the administration of renally excreted cancer drugs or those with established nephrotoxicity.

DESIGN

An International Society for Geriatric Oncology task force was formed to discuss treatment recommendations for this group of patients.

RESULTS

Before drug therapy, the assessment and optimization of hydration status and evaluation of renal function is required. Serum creatinine alone is insufficient as a means of evaluating renal function, and creatinine clearance should at least be calculated in every patient by the abbreviated modification of diet in renal disease or Cockcroft-Gault equations. In the extremes of obesity and cachexia and at very high and low creatinine values, no single tool is really accurate. In these patients, the best estimate of glomerular filtration rate is provided by direct methods such as (51)Cr-EDTA or inulin measurement. Within each drug class, preference may be given to agents less likely to be influenced by renal clearance, which are minimally nephrotoxic, or for which appropriate methods of prevention for renal toxicity exist. Coadministration of known nephrotoxic drugs should be avoided or minimized.

CONCLUSIONS

Future trials should be designed to present data in a way that allows evaluation of the contribution of renal function to toxicity and efficacy.

Impact of creatinine calibration on performance of GFR estimating equations in a pooled individual patient database

BACKGROUND

Variation in performance of glomerular filtration rate (GFR) estimating equations is related to variation in calibration of the creatinine assay across clinical laboratories.

STUDY DESIGN

Cross-sectional analysis.

SETTING & PARTICIPANTS

6 research studies and 4 clinical populations including 5,504 participants who had GFR measured using urinary clearance of iothalamate.

MEASUREMENTS

Standardized serum creatinine values obtained by means of calibration to the Cleveland Clinic Research Laboratory using frozen specimens, a calibration panel, and/or survey results from the College of American Pathologists.

PREDICTOR

Noncalibrated serum creatinine assayed in research and clinical laboratories compared with standardized serum creatinine.

OUTCOME

Difference between measured GFR versus GFR estimated from the Modification of Diet in Renal Disease (MDRD) Study and Cockcroft-Gault equations.

RESULTS

For a noncalibrated serum creatinine value of 1 mg/dL (88.4 micromol/L), standardized serum creatinine value was 0.07 mg/dL (6.2 micromol/L) less than noncalibrated values. In the pooled data set, for the MDRD Study equation, calibration improved median percentage of difference between measured and estimated GFR from 9.0% (interquartile range [IQR], 28%) to 5.8% (IQR, 28%) and improved the percentage of estimates within 30% of measured GFR (P30) from 80% to 83%. The effect of calibration was greater at higher levels of GFR and varied across studies. For the Cockcroft-Gault equation, calibration worsened the median percentage of difference from -2.0% (IQR, 38%) to -11.4% (IQR, 39%), and the P30, from 74% to 69%.

LIMITATIONS

College of American Pathologist samples were used for calibration of clinical populations; calibration factors do not account for drift over time in the serum creatinine assay; calibration cannot account for variation in assay performance among individuals.

CONCLUSION

Calibration improves the performance of the MDRD Study equation. After calibration, larger errors remain for GFR estimates greater than 60 mL/min/1.73 m2 (>1 mL/s/1.73 m2).

Age- and gender-specific reference values of estimated GFR in Caucasians: the Nijmegen Biomedical Study

The Nijmegen Biomedical Study is a population-based cross-sectional study conducted in the eastern part of the Netherlands. As part of the overall study, we provide reference values of estimated glomerular filtration rate (GFR) for this Caucasian population without expressed risk. Age-stratified, randomly selected inhabitants received a postal questionnaire on lifestyle and medical history. In a large subset of the responders, serum creatinine was measured. The GFR was then measured using the abbreviated Modification of Diet in Renal Disease (MDRD) formula. To limit possible bias, serum creatinine was calibrated against measurements performed in the original MDRD laboratory. The study cohort included 2823 male and 3274 female Caucasian persons aged 18-90 years. A reference population of apparently healthy subjects was selected by excluding persons with known hypertension, diabetes, cardiovascular- or renal diseases. This healthy study cohort included 1660 male subjects and 2072 female subjects, of which 869 of both genders were 65 years or older. The median GFR was 85 ml/min/1.73 m(2) in 30-to 34-year-old men and 83 ml/min/1.73 m(2) in similar aged women. In these healthy persons, GFR declined approximately 0.4 ml/min/year. Our study provides age- and gender-specific reference values of GFR in a population of Caucasian persons without identifiable risk.

Reporting of estimated GFR in the primary care clinic

BACKGROUND

Because serum creatinine is an insensitive measure of kidney dysfunction, guidelines have advocated routine use of estimated glomerular filtration rate (eGFR) to identify patients with chronic kidney disease (CKD). Patients with early (stage 3) CKD remain undiagnosed in primary care clinics; therefore, we hypothesized that routine reporting of eGFR in outpatient clinics would improve the recognition and treatment of CKD.

METHODS

A retrospective review of primary care patients was undertaken at the Bronx Veterans Affairs Medical Center, Bronx, New York, before and after the institution of routine eGFR reporting. We evaluated the achievement of diagnostic and therapeutic treatment goals based on the Kidney Disease Outcomes Quality Initiative guidelines (documentation of CKD, urinalysis assessment, blood pressure < 130/80 mm Hg, and renin-angiotensin system blockade) for patients with stage 3 CKD during each period.

RESULTS

Overall, patients with diabetes with early-stage CKD achieved superior treatment rates than similar patients without diabetes. Routine reporting of eGFR improved the documentation and identification of CKD by almost 50%, although absolute improvement was modest. Use of renin-angiotensin system blockers improved minimally, as did blood pressure control. Patients with documented CKD achieved treatment goals more frequently than patients without documented CKD.

CONCLUSION

Routine reporting of eGFR alone modestly improved the identification of patients with CKD without a clinically significant effect on care. For Modification of Diet in Renal Disease Study calculation of eGFR reporting to effect improvements in CKD care, it will be necessary to pair eGFR reporting with provider education to identify these patients and treat them effectively.

Reporting units for therapeutic drug monitoring: a correctable source of potential clinical error

Variation between laboratories and reference sources in the units used for reporting pathology results raises the possibility of medical error. Data submitted to the RCPA Quality Assurance Programs demonstrate wide variation in the units used for reporting therapeutic drug concentrations. This potential source of medical error needs to be addressed by all parties involved in communicating drug concentrations and providing support information.

The accuracy of cystatin C and commonly used creatinine-based methods for detecting moderate and mild chronic kidney disease in diabetes

BACKGROUND

The accuracy of measuring serum cystatin C levels for detecting various stages of chronic kidney disease (CKD) in diabetes is still unclear.

METHODS

In a cross-sectional study of 251 subjects, a reference glomerular filtration rate (GFR) was measured using (99c)Tc-DTPA plasma clearance (iGFR). Multivariate analysis was used to identify independent clinical and biochemical associations with serum cystatin C and iGFR levels. The diagnostic accuracy of cystatin C and commonly used creatinine-based methods of measuring renal function (serum creatinine, the MDRD four-variable and Cockcroft-Gault formulae) for detecting mild and moderate CKD was also compared.

RESULTS

In the entire study population the same five variables, age, urinary albumin excretion rates, haemoglobin, history of macrovascular disease and triglyceride levels were independently associated with both cystatin C and iGFR levels. A serum cystatin C level cut-off > 82.1 nmol/l (1.10 mg/l) had the best test characteristics as a screening tool for detecting moderate CKD (< 60 ml/min per 1.73 m(2)) when compared with creatinine-based methods. At the upper threshold for mild CKD (< 90 ml/min per 1.73 m(2)), cystatin C also had greater diagnostic accuracy than creatinine, but had similar diagnostic accuracy when compared with creatinine-based formulae for predicting renal function.

CONCLUSIONS

This study suggests that the clinical and biochemical parameters associated with serum cystatin C levels are closely linked to those associated with GFR and highlights the potential usefulness of screening for moderate or mild CKD in subjects with diabetes by simply measuring serum cystatin C levels.

Impact of gender on outcomes in chronic systolic heart failure

BACKGROUND AND AIM

Understanding the influence of gender in heart failure allows for better treatment. This study described the gender differences in heart failure patients and their response to therapy.

METHODS

Consecutive patients (116 men vs. 52 women) from 1997 to 2002 were recruited from a single heart failure unit. Mean follow-up was 40+/-19 months.

RESULTS

Mean age was 68+/-12 years; left ventricular ejection fraction (LVEF) 27+/-12%. Women had higher mean LVEF, left ventricular end-diastolic diameter, and worse New York Heart Association (NYHA) functional class at baseline compared to men, while age, body mass index, blood pressure, estimated glomerular filtration rate and other co-morbidities did not differ significantly. Fewer women remained on angiotensin-converting-enzyme inhibitors while angiotensin-II-receptor blockers use increased significantly. By the end of the study, both genders exhibited similar magnitude of improvements in LVEF, cardiac dimensions, hemodynamics and mean NYHA functional class. In multivariate analysis, NYHA functional class was the strongest predictor of mortality: patients with NYHA class III/IV at baseline had 2.4-fold increased mortality risk compared to those in NYHA class I/II (95% CI 1.09-5.51, p=0.03). For men, functional class at baseline was the strongest predictor of mortality while for women, it was age at baseline.

CONCLUSIONS

In a contemporary tertiary referral heart failure clinic, women were observed to have better LVEF, but worse NYHA functional class than men. Both genders exhibited functional and hemodynamic improvements with only minor differences in their medical therapies. Predictors of mortality differed between the genders.

International Society of Geriatric Oncology (SIOG) recommendations for the adjustment of dosing in elderly cancer patients with renal insufficiency

A SIOG taskforce was formed to discuss best clinical practice for elderly cancer patients with renal insufficiency. This manuscript outlines recommended dosing adjustments for cancer drugs in this population according to renal function. Dosing adjustments have been made for drugs in current use which have recommendations in renal insufficiency and the elderly, focusing on drugs which are renally eliminated or are known to be nephrotoxic. Recommendations are based on pharmacokinetic and/or pharmacodynamic data where available. The taskforce recommend that before initiating therapy, some form of geriatric assessment should be conducted that includes evaluation of comorbidities and polypharmacy, hydration status and renal function (using available formulae). Within each drug class, it is sensible to use agents which are less likely to be influenced by renal clearance. Pharmacokinetic and pharmacodynamic data of anticancer agents in the elderly are needed in order to maximise efficacy whilst avoiding unacceptable toxicity.

High prevalence and low awareness of CKD in Taiwan: a study on the relationship between serum creatinine and awareness from a nationally representative survey

BACKGROUND

The burden of chronic kidney disease (CKD) is a global challenge. Empirical evidence of low CKD awareness rates in developed countries speaks for an urgent need to strengthen strategies for CKD identification and prevention. The aim of this study is to estimate the awareness rate of CKD in Taiwan to promote early detection of CKD in this country.

METHODS

Data from a nationally representative survey were used for analysis. The study included 6,001 subjects. The simplified Modification of Diet in Renal Disease equation was used to define glomerular filtration rate (GFR) and CKD stages according to criteria of the US National Kidney Foundation. Descriptive methods were used to analyze data.

RESULTS

The prevalence of CKD stages 3 to 5 in Taiwan is 6.9% (95% confidence interval, 4.4 to 9.4). Awareness rates for CKD in Taiwan are low: 8.0% for individuals with stage 3, 25.0% for those with stage 4, and 71.4% for those with stage 5. Awareness rate is related closely to serum creatinine level: those with creatinine levels greater than 1.6 mg/dL (>141 micromol/L) are more likely to be informed of having a kidney disease.

CONCLUSION

The high prevalence and low awareness of CKD in Taiwan explicitly show the need to advocate more strongly for CKD prevention and education for both physicians and the populace. Establishment of a mandated automatic GFR reporting system may be the first priority we need to accomplish in Taiwan to improve kidney well-being.

Predictive Value of a Positive Fecal Occult Blood Test Increases as the Severity of CKD Worsens

BACKGROUND

Because chronic kidney disease (CKD) may be associated with gastrointestinal bleeding from trivial mucosal lesions, we hypothesized that the predictive value of a positive fecal occult blood test (FOBT) result for clinically important colonic lesions would decrease as the stage of CKD worsened.

METHODS

We prospectively identified 1,225 consecutive asymptomatic average-risk patients who were referred for colonoscopy to evaluate a positive FOBT result. Using the Modification of Diet in Renal Disease equation, we estimated glomerular filtration rate (GFR) and staged the severity of CKD by using standard criteria as follows: normal/stage 1 (GFR > or = 90 mL/min/1.73 m2 [> or = 1.50 mL/s]), stage 2/3 (GFR 30 to 89 mL/min/1.73 m2 [0.50 to 1.48 mL/s]), and stage 4/5 (GFR < 30 mL/min/1.73 m2 [< 0.50 mL/s] or dialysis).

RESULTS

Clinically important lesions were identified in 23.9% of 531 individuals with none/stage 1 CKD, 32.8% of 497 subjects with stage 2/3 CKD, and 42.6% of 197 patients with stage 4/5 CKD (P < 0.001). Compared with patients with none/stage 1 CKD, adjusted odds of identifying a clinically important lesion were 1.61 (95% confidence interval, 1.21 to 2.15) in subjects with stage 2/3 CKD and 2.33 (95% confidence interval, 1.62 to 3.36) in patients with stage 4/5 CKD. Prevalences of adenomas of 1 cm or greater (15.1% versus 20.1% versus 22.8%; P = 0.007), carcinomas (5.1% versus 10.1% versus 13.2%; P < 0.001), and vascular ectasias (1.7% versus 2.4% versus 6.1%; P = 0.003) increased with the severity of CKD.

CONCLUSION

Contrary to our initial hypothesis, we found that the predictive value of a positive FOBT result for clinically important colonic lesions increased as the severity of CKD worsened.

The assessment of kidney function by general practitioners in Australian patients with type 2 diabetes (NEFRON-2)

OBJECTIVE

To examine factors influencing the identification of kidney impairment in patients with type 2 diabetes in Australian primary care.

DESIGN, SETTING AND PARTICIPANTS

348 general practitioner investigators were asked to estimate kidney function and its severity in 10-15 consecutively presenting patients with type 2 diabetes (n = 3893). They were then asked, for each patient, whether they routinely estimated kidney function. No instruction was provided on how kidney function should be estimated or categorised. Data were collected between April and September 2005.

MAIN OUTCOME MEASURES

Kidney function estimated by the Cockcroft-Gault equation using clinical and laboratory data provided by the GP; estimates of kidney function made by the GP.

RESULTS

In 24% of the patients with type 2 diabetes, their GP routinely estimated kidney function. However, few of these patients had impaired kidney function or risk factors for kidney disease. There was a good statistical correlation between the estimates made by GPs and the data-derived estimates (R2 = 0.72). GPs identified patients with data-derived estimates of kidney function < 60 mL/min in over 83% of cases, with a specificity of 90%. Impaired kidney function was reported by GPs in 34.4% of men and 36.4% of women. These figures were discordant with function categorisation using both GP estimates and data-derived values, overlapping in half of the patients. Despite GPs' ability to assess creatinine clearance, "raw" (unstandardised) serum creatinine levels inappropriately influenced the perception of impairment of kidney function.

CONCLUSION

GPs can accurately assess kidney function, without reporting of estimated glomerular filtration rate (eGFR). However, even in patients at increased risk of chronic kidney disease, routine estimates are seldom made. Our findings underline the value of the recent initiative recommending automatic reporting of eGFR in Australia.

The burden of chronic kidney disease in Australian patients with type 2 diabetes (the NEFRON study)

OBJECTIVE

To estimate the frequency of chronic kidney disease (CKD) in a clinic-based sample of patients with type 2 diabetes in the setting of Australian primary care.

DESIGN, SETTING AND PARTICIPANTS

Expressions of interest were invited from all registered general practitioners in Australia: 500 GP investigators were randomly selected from each stratum (state and urban versus rural location), proportional to the census population, and asked to recruit and provide data for 10-15 consecutively presenting adults with type 2 diabetes between April and September 2005.

MAIN OUTCOME MEASURES

Estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73 m(2) and evidence of kidney damage on urinalysis (eg, microalbuminuria).

RESULTS

348 GP investigators submitted data for 3893 individuals with type 2 diabetes (52% men; median age, 66 years). Almost one in every four patients consulting their GPs had an eGFR < 60 mL/min/1.73 m(2) (23.1%; 95% CI, 21.8%-24.5%). More than one in three had an elevated urinary albumin-creatinine ratio (ACR) (34.6%; 95% CI, 33.3%-35.9%). There was an overlap of 10.4% of patients with both an eGFR < 60 mL/min/1.73 m(2) and an elevated urinary ACR, meaning that almost one in two patients with type 2 diabetes consulting their GPs (47.1%; 95% CI, 45.8%-48.4%) had CKD. CKD was significantly more common in women, in older people, and in individuals with established macrovascular disease.

CONCLUSION

CKD is a common complication of type 2 diabetes, found in about half of all patients with type 2 diabetes consulting their GPs. Efforts to increase the recognition of CKD will lead to improved care, and possibly survival, of patients with type 2 diabetes.

Using standardized serum creatinine values in the modification of diet in renal disease study equation for estimating glomerular filtration rate

BACKGROUND

Glomerular filtration rate (GFR) estimates facilitate detection of chronic kidney disease but require calibration of the serum creatinine assay to the laboratory that developed the equation. The 4-variable equation from the Modification of Diet in Renal Disease (MDRD) Study has been reexpressed for use with a standardized assay.

OBJECTIVE

To describe the performance of the revised 4-variable MDRD Study equation and compare it with the performance of the 6-variable MDRD Study and Cockcroft-Gault equations.

DESIGN

Comparison of estimated and measured GFR.

SETTING

15 clinical centers participating in a randomized, controlled trial.

PATIENTS

1628 patients with chronic kidney disease participating in the MDRD Study.

MEASUREMENTS

Serum creatinine levels were calibrated to an assay traceable to isotope-dilution mass spectrometry. Glomerular filtration rate was measured as urinary clearance of 125I-iothalamate.

RESULTS

Mean measured GFR was 39.8 mL/min per 1.73 m2 (SD, 21.2). Accuracy and precision of the revised 4-variable equation were similar to those of the original 6-variable equation and better than in the Cockcroft-Gault equation, even when the latter was corrected for bias, with 90%, 91%, 60%, and 83% of estimates within 30% of measured GFR, respectively. Differences between measured and estimated GFR were greater for all equations when the estimated GFR was 60 mL/min per 1.73 m2 or greater.

LIMITATIONS

The MDRD Study included few patients with a GFR greater than 90 mL/min per 1.73 m2. Equations were not compared in a separate study sample.

CONCLUSIONS

The 4-variable MDRD Study equation provides reasonably accurate GFR estimates in patients with chronic kidney disease and a measured GFR of less than 90 mL/min per 1.73 m2. By using the reexpressed MDRD Study equation with the standardized serum creatinine assay, clinical laboratories can report more accurate GFR estimates.

Evaluation of predictive formulae for glomerular filtration rate for carboplatin dosing in gynecological malignancies

OBJECTIVES

Carboplatin dosing is usually based on glomerular filtration rate (GFR). The Cockcroft-Gault and the Modified Diet in Renal Disease (MDRD) Study formulae are based on serum creatinine to estimate GFR when measured GFR is impractical. The MDRD formula has been shown to be more accurate in non-cancer patients with chronic renal disease. We compared the accuracy of these formulae for dosing carboplatin in patients with gynecological cancers.

METHODS

Patient data were collected retrospectively at the Vancouver Centre of the British Columbia Cancer Agency, Canada. GFR estimated by formula was compared to measured GFR. Dose derived from estimated GFR was compared to dose derived from measured GFR. Bias (percentage error) and precision (absolute percentage error) were compared with two-sided paired t-test.

RESULTS

A total of 96 patients were evaluable: median age 60 years, weight 62 kg, height 159 cm, baseline serum creatinine 71 micromol/l, GFR 91 ml/min. Both formulae had limited precision with a small bias for estimated GFR and dosing. Eight-five percent of patients would have received a significantly different dose if estimated GFR from any formula was used. The MDRD formula was more precise than the Cockcroft-Gault formula.

CONCLUSIONS

The MDRD formula seems to be more accurate than the Cockcroft-Gault formula in this population. However, both have limited precision and measured GFR should be preferred for carboplatin dosing.

Estimating glomerular filtration rate in diabetes: a comparison of cystatin-C- and creatinine-based methods

AIMS/HYPOTHESIS

We compared the predictive performance of a GFR based on serum cystatin C levels with commonly used creatinine-based methods in subjects with diabetes.

SUBJECTS, MATERIALS AND METHODS

In a cross-sectional study of 251 consecutive clinic patients, the mean reference (plasma clearance of (99m)Tc-diethylene-triamine-penta-acetic acid) GFR (iGFR) was 88+/-2 ml min(-1) 1.73 m(-2). A regression equation describing the relationship between iGFR and 1/cystatin C levels was derived from a test population (n=125) to allow for the estimation of GFR by cystatin C (eGFR-cystatin C). The predictive performance of eGFR-cystatin C, the Modification of Diet in Renal Disease 4 variable formula (MDRD-4) and Cockcroft-Gault (C-G) formulas were then compared in a validation population (n=126).

RESULTS

There was no difference in renal function (ml min(-1) 1.73 m(-2)) as measured by iGFR (89.2+/-3.0), eGFR-cystatin C (86.8+/-2.5), MDRD-4 (87.0+/-2.8) or C-G (92.3+/-3.5). All three estimates of renal function had similar precision and accuracy.

CONCLUSIONS/INTERPRETATION

Estimates of GFR based solely on serum cystatin C levels had the same predictive potential when compared with the MDRD-4 and C-G formulas.

Is nonalbuminuric renal insufficiency in type 2 diabetes related to an increase in intrarenal vascular disease?

OBJECTIVE

To investigate the role of intrarenal vascular disease in the pathogenesis of nonalbuminuric renal insufficiency in type 2 diabetes.

RESEARCH DESIGN AND METHODS

We studied 325 unselected clinic patients who had sufficient clinical and biochemical information to calculate an estimated glomerular filtration rate (eGFR) using the Modified Diet in Renal Disease six-variable formula, at least two estimations of urinary albumin excretion rates (AER), and a renal duplex scan to estimate the resistance index of the interlobar renal arteries. The resistance index, measured as part of a complications surveillance program, was compared in patients with an eGFR < or >or=60 ml/min per 1.73 m(2) who were further stratified into normo- (AER <20), micro- (20-200), or macroalbuminuria (> 200 microg/min) categories.

RESULTS

Patients with an eGFR <60 ml/min per 1.73 m(2) had a higher resistance index of the renal interlobar arteries compared with patients with an eGFR >or=60 ml/min per 1.73 m(2). However, the resistance index was elevated to a similar extent in patients with an eGFR <60 ml/min per 1.73 m(2) regardless of albuminuric status (normo- 0.74 +/- 0.01, micro- 0.73 +/- 0.01, and macroalbuminuria resistance index 0.75 +/- 0.11). Multiple regression analysis revealed that increased age (P < 0.0001), elevated BMI (P = 0.0001), decreased eGFR (P < 0.01), and decreased diastolic blood pressure (P < 0.01), but not an increased AER, were independently associated with an elevated resistance index in patients with impaired renal function.

CONCLUSIONS

Subjects with type 2 diabetes and reduced glomerular filtration rate had similar degrees of intrarenal vascular disease, as measured by the intrarenal arterial resistance index, regardless of their AER status. The pathological mechanisms that determine the relationship between impaired renal function and AER status in subjects with type 2 diabetes remain to be elucidated.

Does the ID-MS traceable MDRD equation work and is it suitable for use with compensated Jaffe and enzymatic creatinine assays?

BACKGROUND

International recommendations suggest that measurement of serum creatinine should be supplemented with an estimate of glomerular filtration rate (GFR) using the Modification of Diet in Renal Disease (MDRD) study equation. One problem has been the lack of standardization of commercially available creatinine assays resulting in varying estimates of GFR. A revision of the MDRD equation offers traceability to a reference method. This study evaluates the use of isotope dilution mass spectrometry (ID-MS), the compensated Jaffe and enzymatic creatinine methods compared with the Beckman CX3 Jaffe assay used to derive the MDRD equation and investigates their impact on GFR estimation using both the original and ID-MS-traceable MDRD equations.

METHODS

Serum creatinine was measured in 277 patients by (i) ID-MS, (ii) a Roche enzymatic assay, (iii) a Roche compensated kinetic Jaffe assay and (iv) a Beckman CX3 kinetic Jaffe assay. Estimated GFR was calculated using the MDRD equations.

RESULTS

The ID-MS (-7.5%), Roche enzymatic (-8.6%) and compensated kinetic Jaffe (-11.9%) assays were all negatively biased (P < 0.0001) compared with the Beckman CX3 assay, causing predictable, clinically significant, overestimation of GFR when the original MDRD equation is used. This positive bias was reduced (ID-MS 6.7 to 0.4%; enzymatic 8.8 to 3.4%; compensated kinetic Jaffe 13.7 to 7.1%) when GFRs were calculated using the ID-MS-traceable MDRD equation.

CONCLUSIONS

Compensated assays that account for non-creatinine chromogen interference produce significantly higher estimates of GFR when using the original MDRD equation. Use of the ID-MS-traceable MDRD equation ameliorates this effect. There is good agreement between estimated GFR derived from the original MDRD equation using Beckman Astra CX3 data and estimated GFR derived from the new ID-MS-traceable MDRD equation using a local ID-MS creatinine assay. This suggests that the ID-MS-traceable MDRD equation may be reliably used with both ID-MS and true ID-MS-traceable creatinine assays without the requirement for standardization to the MDRD laboratory.

Plasma levels of asymmetric dimethylarginine (ADMA) are related to intima-media thickness of the carotid artery: an epidemiological study

Asymmetric dimethylarginine (ADMA) is a circulating endogenous nitric oxide (NO) synthase inhibitor. It has been reported that plasma levels of ADMA are related to intima-media thickness (IMT) in small numbers. We investigated this issue in a large number of subjects without overt cerebro-cardiovascular diseases. A total of 712 subjects (305 men and 407 women; age, 62.6+/-11.2 years) received a health examination in 1999 in a farming community. We measured blood pressure (BP), blood chemistries, and fasting plasma total ADMA levels. IMT of the common carotid artery was determined with the use of duplex ultrasonography as an index of atherosclerosis. Uni- and multi-variate analyses for determinants of IMT were performed. For the total population, the mean ADMA level was 0.50 micromol/l. By the use of multiple stepwise regression analysis, IMT was significantly associated with ADMA (p<0.01), age (p<0.001), and systolic BP (p<0.001). Furthermore, when IMT was analyzed across the ADMA tertiles after adjustments for age, sex, and other confounders, analysis of co-variance showed a significant (p<0.001) and linear association between IMT and ADMA levels. In conclusion, our study indicates that plasma level of ADMA is a strong and independent determinant of IMT of the carotid artery in the large number of subjects without overt cerebro-cardiovascular diseases.

Cardiovascular Drug Therapy in Elderly Patients

An increasing number of elderly patients are exposed to cardiovascular drugs for the treatment of acute and/or chronic conditions. This is a result of the progressive aging of the population, a common feature in most industrialised countries, and an improvement in primary and secondary cardiovascular prevention strategies with increased survival rates. Traditionally, most elderly patients receiving cardiovascular drugs had advanced cardiac, liver and kidney disease that significantly influenced drug pharmacokinetic and pharmacodynamic parameters. Currently, however, many patients without significant organ impairment receive cardiovascular therapy for primary or early secondary prevention (i.e. increased vascular risk, asymptomatic left ventricular dysfunction, poststroke phase, type 2 diabetes mellitus), highlighting the need for a better understanding of specific age-related pharmacokinetic and pharmacodynamic effects. A systematic review has been conducted on the specific effects of aging, in the absence of major co-morbidities, on the pharmacokinetic and pharmacodynamic properties of traditional and newer cardiovascular drugs. Currently, the evidence available is poor or nonexisting for several drugs and mainly derived from very small and underpowered studies, thus limiting data interpretation. In particular, there is very little information on patients >80 years of age, thus raising important concerns about the correct use of these drugs in this constantly growing population.