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Original Investigation |

Serum Creatinine Is an Inadequate Screening Test for Renal Failure in Elderly Patients FREE

Peter J. Swedko, MD; Heather D. Clark, MD, CM, MSc; Koushi Paramsothy, MD; Ayub Akbari, MD
[+] Author Affiliations

From the Division of Nephrology (Drs Swedko and Akbari), Department of Medicine (Drs Swedko, Clark, Paramsothy, and Akbari), The Ottawa Hospital, and the Kidney Research Centre (Drs Swedko and Akbari) and the Clinical Epidemiology Unit (Dr Clark), Ottawa Health Research Institute, Ottawa, Ontario.


Arch Intern Med. 2003;163(3):356-360. doi:10.1001/archinte.163.3.356.
Text Size: A A A
Published online

Background  Serum creatinine is the most commonly used screening test for renal failure. We hypothesized that serum creatinine would underestimate the degree of renal failure in elderly people because they have a reduced muscle mass. If so, this would lead to underrecognition and thus suboptimal care of patients with severe renal failure.

Methods  We conducted a retrospective medical record review of all patients 65 years or older in an outpatient academic family medicine practice. The glomerular filtration rate was calculated using the Cockcroft and Gault formula and was used to evaluate the testing characteristics of serum creatinine for the detection of renal failure.

Results  We screened 1510 patients, 854 (56.6%) of whom met the inclusion criteria. Renal failure (glomerular filtration rate, ≤50 mL/min) was present in 28.9% of the patients, and severe renal failure (Cockcroft and Gault formula glomerular filtration rate, ≤30 mL/min) was present in 6.4%. A serum creatinine level of greater than 1.7 mg/dL (>150 µmol/L) had a sensitivity of 12.6% and a specificity of 99.9% for the detection of renal failure. For the detection of severe renal failure, the sensitivity was 45.5%, with a 99.1% specificity. Only 15 (27.3%) of the 55 patients with severe renal failure were referred to a nephrologist. Moreover, 34 (85%) of the 40 nonreferred patients with severe renal failure were incompletely evaluated regarding the metabolic complications associated with kidney dysfunction.

Conclusion  Serum creatinine is a poor screening test for renal failure in elderly patients, leading to marked underinvestigation and underrecognition of renal failure in this population.

Figures in this Article

THE PREVALENCE of end-stage renal disease (ESRD) is increasing at an alarming rate. In Canada, the number of patients receiving renal replacement therapy was 17 807 as of December 31, 1996, and is projected to be 32952 by 2006.1 Data from the United States predict that the 304 083 patients with ESRD registered in 1997 will have doubled by 2010.2 Elderly patients have the highest incidence rates of ESRD, and their proportion of the population undergoing long-term dialysis is increasing.3,4 Early referral to a nephrologist, or to a multidisciplinary team specializing in ESRD care, has been associated with a reduction in health care costs, morbidity, and mortality in patients starting renal replacement therapy.510 Such timely referral requires early detection of kidney disease, and in this respect the most common screening test for renal dysfunction is the serum creatinine.11 Recently published clinical practice guidelines12 acknowledge these facts by addressing the evaluation and referral of patients with elevated levels of serum creatinine.

Unfortunately, serum creatinine alone may be misleading when evaluating renal dysfunction. For instance, patients with a relatively lower muscle mass, such as women and/or elderly persons, can have a serum creatinine level within the laboratory-reported normal range, although their renal function is severely compromised.11 More accurate estimates of renal function can be obtained in clinical practice by measuring creatinine clearance from a timed urine collection or by using formulas, such as the Cockcroft and Gault formula (C-G),13 to calculate the glomerular filtration rate (GFR).11

We hypothesized that renal failure is not being detected in many elderly patients because their serum creatinine levels fall within or only slightly above the laboratory-reported normal range, and that these patients do not undergo an appropriate evaluation or receive referral in a timely manner. A study was, therefore, designed to evaluate the detection and management of renal failure in ambulatory elderly patients within the primary care setting.

This study, approved by the Research Ethics Board of The Ottawa Hospital, is a retrospective medical record review, with data collected between August 1 and November 1, 2000.

PATIENT SELECTION

All patients 65 years or older in an academic family medicine practice associated with The Ottawa Hospital, a tertiary care teaching hospital, were identified using a computer-generated list obtained from the main practice database. Patients were excluded from the study for the following reasons: (1) a serum creatinine level had never been documented in the medical record, (2) the patient's weight had never been documented in the medical record, (3) the elapsed time between the measurement of the serum creatinine level and the measurement of the patient's weight was longer than 10 years, (4) the patient was undergoing hemodialysis or peritoneal dialysis at the time of review, or (5) the medical record was not available for review during the study period.

DATA COLLECTION

The following data were recorded for each patient: age, sex, most recent serum creatinine level, and weight. The C-G was used to calculate the GFR.13 This formula has been validated in elderly populations to accurately predict the measured creatinine clearance and the glomerular filtration rate.1416 The C-G GFR has also been superior to measured creatinine clearance as a predictor of glomerular filtration rate in several studies.1719

Renal failure was defined as a C-G GFR of 50 mL/min or less. This value was chosen to represent a decreased GFR that would not be attributable to normal aging alone.20 Severe renal failure was defined as a C-G GFR of 30 mL/min or less. At this level of renal function, prompt referral to a nephrologist for ongoing management has proved beneficial.510,12

Additional data were sought in the severe renal failure category: (1) blood pressure, (2) history of diabetes mellitus, and (3) whether the patient was referred to a nephrologist. We also determined whether these patients underwent the following investigations: the determination of hemoglobin, serum bicarbonate, serum calcium, serum phosphate, and serum albumin levels; chemical urinalysis; measured creatinine clearance; and abdominal ultrasonography.

OUTCOMES

The primary outcome evaluated was the value of serum creatinine as a test for renal failure in an elderly primary care population. We selected a serum creatinine level of 1.7 mg/dL (150 µmol/L) as a clinically relevant cutoff value, and any higher value was considered a positive test result for renal failure. This conservative cutoff value was selected based on previous studies,21,22 which demonstrated that family physicians were unlikely to refer patients to a nephrologist when the serum creatinine level was 1.7 mg/dL or less. The serum creatinine level was compared with the C-G GFR to determine its characteristics as a test for renal failure.

Secondary outcomes were the prevalence of renal failure in this population, the pattern of nephrology consultation for patients with severe renal failure, and the pattern of investigation and management of causes and complications of severe renal failure.

STATISTICAL ANALYSES

Results are presented as mean ± SD. Statistical analysis was performed using Statistical Product and Service Solution software, version 10 (SPSS Inc, Chicago, Ill). The t test for continuous variables and the χ2 test for categorical variables were used where indicated. Logistic regression was performed to identify characteristics that predicted referral to a nephrologist. P<.05 was considered statistically significant.

There were 1510 patients 65 years or older with active medical records, 1315 of which were available for review. Of these records, 461 were excluded (277 did not have a documented creatinine level, and 184 had a documented serum creatinine level but did not have a documented weight), leaving a study population of 854 patients (Figure 1). The mean age and the male-female ratio were not significantly different in the included and excluded patients (P = .16 for age; P = .09 for sex; data not shown).

Place holder to copy figure label and caption
Figure 1.

Flowchart of the study design and results. C-G GFR indicates glomerular filtration rate estimated by the Cockcroft and Gault formula.

Graphic Jump Location

The characteristics of the 854 patients are summarized in Table 1. There were 380 men (44.5%) and 474 women (55.5%). Women had a significantly lower C-G GFR than men, despite having a lower serum creatinine level.

PREVALENCE OF RENAL FAILURE

Renal failure (C-G GFR ≤50 mL/min) was present in 28.9% of the patients, while severe renal failure (C-G GFR ≤30 mL/min) was present in 6.4% of the patients (Figure 1). The prevalence of renal failure was significantly higher in women than in men (164 [34.6%] of 474 women vs 83 [21.8%] of 380 men; P<.001). There was also a higher prevalence of severe renal failure in women than in men, but the increase did not reach statistical significance (37 [7.8%] of 474 women vs 18 [4.7%] of 380 men; P = .10).

SERUM CREATININE AS A TEST FOR RENAL FAILURE

For the detection of renal failure, a serum creatinine level of 1.7 mg/dL had an overall sensitivity of only 12.6% (Table 2). In fact, 87.4% of the patients with renal failure had serum creatinine values of 1.7 mg/dL or lower. The serum creatinine performed better in the detection of severe renal failure; however, the sensitivity was only 45.5% (Table 2). Also, the test was inconsistent across sex. Interestingly, although the mean serum creatinine level of women with severe renal failure was significantly lower than that of men, the C-G GFR was similar (Figure 2). Of the 55 patients with severe renal failure, 30 (54.5%) had serum creatinine values of 1.7 mg/dL or less.

Table Graphic Jump LocationTable 2. Characteristics of Serum Creatinine as a Test for Renal Failure*
Place holder to copy figure label and caption
Figure 2.

Comparison of serum creatinine level in the 55 men and women with severe renal failure (Cockcroft and Gault formula glomerular filtration rate [C-G GFR], ≤30 mL/min). Women had significantly lower mean serum creatinine values than men, despite a similar level of renal function. This is likely because of the smaller muscle mass of women compared with men, as suggested by the women's significantly lower mean weight. The asterisk indicates P<.005. To convert creatinine to milligrams per deciliter, divide by 88.4.

Graphic Jump Location
REFERRAL TO A NEPHROLOGIST

Only 15 (27.3%) of the 55 patients with severe renal failure were referred to a nephrologist. Patients with higher serum creatinine levels were significantly more likely to be referred to a nephrologist; the odds of being referred increased by 2.4 for each 0.23-mg/dL (20-µmol/L) increase in serum creatinine level (P = .001). Not a single patient with severe renal failure and a serum creatinine value of 1.7 mg/dL or less was referred to a nephrologist. Men were more likely to be referred (odds ratio, 10.0; 95% confidence interval, 2.5-40.3; P = .001), as were diabetic patients (odds ratio, 5.3; 95% confidence interval, 1.4-19.8; P = .01), although the referral rate for diabetic patients was still only 50% (8 patients referred of 16 patients with diabetes mellitus).

PRIMARY CARE EVALUATION OF PATIENTS WITH SEVERE RENAL FAILURE

The data from the 40 patients with severe renal failure who were not referred to a nephrologist were analyzed further, to examine the management of severe renal failure in the primary care setting (Figure 3). Of these 40 nonreferred patients, 27 (67.5%) underwent a urinalysis, 14 (35%) underwent abdominal ultrasonography, and only 7 (17.5%) had a 24-hour urine collection for creatinine clearance. Hemoglobin was measured in all 40 (100%) of these patients, serum calcium level in 14 (35%), serum bicarbonate level in 18 (45%), serum albumin level in 11 (27.5%), and serum phosphate level in 3 (7.5%). Anemia (defined as a hemoglobin level <13.0 g/dL in men and <11.5 g/dL in women) was present in 3 (37.5%) of 8 men and 6 (18.8%) of 32 women who were not referred.

Place holder to copy figure label and caption
Figure 3.

Investigation for causes and complications of severe renal failure (Cockcroft and Gault formula glomerular filtration rate, ≤30 mL/min) in the 40 nonreferred patients.

Graphic Jump Location

The mean blood pressure values for all 55 patients with severe renal failure were 144 ± 21 mm Hg (systolic) and 74 ± 9 mm Hg (diastolic). There were no significant differences between the mean blood pressure values of referred and nonreferred patients (145/73 vs 143/74 mm Hg; P = .76 for systolic; P = .51 for diastolic). Suboptimal blood pressure control, defined as a mean blood pressure higher than 130/80 mm Hg,23 was noted in 43 (78.2%) of the patients with severe renal failure.

These data convincingly demonstrate the poor sensitivity of serum creatinine alone for the detection of renal failure in ambulatory elderly patients. We also observed that family physicians tended not to investigate or refer many patients with severe renal failure, underscoring the problems of relying on this poorly sensitive test. Of further interest was the high prevalence of renal failure in our study population, with an intriguing female preponderance.

We based our sensitivity analysis on a serum creatinine level of 1.7 mg/dL, although the selection of a lower cutoff value would have increased the sensitivity of the test for the detection of renal failure. The goal of this study was to evaluate the performance of the serum creatinine level in its clinical context, as primary care practitioners are applying it. This cutoff value was chosen based on 2 previous studies, by Mendelssohn and colleagues21 and by Wilson and colleagues.22 They found that physicians were most likely to refer a patient to a nephrologist when the serum creatinine level was greater than 3.39 mg/dL (300 µmol/L), and tended not to refer patients whose serum creatinine level was 1.35 to 1.69 mg/dL (120-150 µmol/L).

The investigation for causes and complications of severe renal failure by the family physicians in our study was poor. Only 15 (27.3%) of the 55 patients with severe renal failure were referred to a nephrologist, and few of the nonreferred patients were investigated for the metabolic complications of renal failure, suggesting that the renal failure was not recognized. One of the major determinants of referral in patients with severe renal failure (C-G GFR, ≤30 mL/min) was the serum creatinine level; the odds of nephrology referral increased significantly with higher serum creatinine values, yet there were no nephrology referrals made for patients with serum creatinine levels of 1.7 mg/dL or less. The family physicians seemed to base their management decisions on the serum creatinine levels irrespective of the patients' true renal function.

Other researchers have commented on the risks of using serum creatinine alone to detect renal disease in elderly patients. Duncan and colleagues20 used a cutoff value of 1.47 mg/dL (130 µmol/L) or greater to define an elevated serum creatinine level, and found that 47.3% of those 70 years and older with a "normal" serum creatinine level had a C-G GFR of 50 mL/min or less. A similar study by Papaioannou and colleagues24 focused on patients 65 years and older living in long-term care facilities, and found that their mean C-G GFR was only 43 mL/min while their mean serum creatinine level was 0.97 mg/dL (86 µmol/L), within the normal range. Our study confirms and extends these observations by demonstrating the underinvestigation and lack of referral of elderly patients with renal disease. This is all the more important given the increasing incidence of ESRD in this population.

Of interest was the high prevalence of renal failure in elderly women. Papaioannou and colleagues,24 who used the C-G GFR and not the serum creatinine to detect renal failure, found that the prevalence of a C-G GFR of 50 mL/min or less was 44% in men and 69% in women 65 years or older. These results conflict with earlier studies4,25,26 demonstrating a much lower overall prevalence of renal failure, with a male preponderance. Each of these earlier studies used the serum creatinine level to detect renal failure in their respective study populations. Interestingly, we found that the serum creatinine level was much less sensitive for the detection of renal failure in women than it was in men. The true prevalence of renal failure in women was likely underestimated in previous studies because the serum creatinine level, and not the glomerular filtration rate, was used as a marker of kidney function.

We observed that elderly women with severe renal failure were significantly less likely to be referred to a nephrologist. In Canada and the United States, more men than women start dialysis each year.27,28 Several researchers2932 have explored the existence of sex bias in access to dialysis and transplantation, but the potential sources of this bias are not well delineated. It is conceivable that renal failure is being underrecognized in elderly women because of the use of the serum creatinine level and, therefore, these women are not referred for dialysis or transplantation. Clearly, this is an area that requires further study.

One limitation of this study is the failure to use a gold standard measurement of glomerular filtration rate, such as inulin clearance, a limitation predicated, among other things, by the retrospective nature of the study. We, therefore, selected the C-G GFR as our standard measurement of renal function. The Cockcroft and Gault formula estimates glomerular filtration rate from the age, weight, sex, and serum creatinine level of the patient, and has the advantage of being easily applied in the clinical setting.13 It has been validated in elderly patients, and accurately predicts the measured creatinine clearance and the glomerular filtration rate.1416 Some researchers33,34 dispute the use of the C-G GFR in elderly patients, based on a few negative study results; these studies involve few patients and use the 24-hour urine collection for creatinine clearance as the reference standard. The C-G GFR has been shown to be superior to 24-hour urine measured for creatinine clearance as a predictor of glomerular filtration rate in several studies.1719

We conclude that serum creatinine, as it is being used by primary care practitioners to screen geriatric populations, is a seriously flawed test. This leads to a lack of appropriate investigation and referral of many elderly patients with renal failure, which may increase their risk of morbidity and mortality. The estimation or measurement of glomerular filtration rate should be the preferred screening method for the detection of renal failure in elderly patients.

Corresponding author and reprints: Ayub Akbari, MD, Division of Nephrology, The Ottawa Hospital, Riverside Campus, 1967 Riverside Dr, Ottawa, Ontario, Canada K1H 7W9 (e-mail: aakbari@ottawahospital.on.ca).

Accepted for publication June 14, 2002.

This study was supported by a grant from Ortho Biotech Inc, Raritan, NJ.

We thank Kevin D. Burns, MD, and Marshall D. Lindheimer, MD, for their expert advice, and the physicians of the Family Medicine Center, The Ottawa Hospital, Civic Campus, Ottawa, Ontario, for their help.

Schaubel  DEMorrison  HIDesmeules  MParsons  DAFenton  SS End-stage renal disease in Canada: prevalence projections to 2005. CMAJ. 1999;1601557- 1563
Collins  AXue  JMa  J Estimating the number of patients & Medicare costs for ESRD in the US to 2010 [online publication]. US Renal Data System Web site. Available at: http://www.usrds.org. Accessed September 25, 2001.
Giuseppe  PMario  SBarbara  PG  et al.  Elderly patients on dialysis: epidemiology of an epidemic. Nephrol Dial Transplant. 1996;11 (suppl 9) 26- 30
Link to Article
Jungers  PChauveau  PDeschamps-Latscha  B  et al.  Age and gender-related incidence of chronic renal failure in a French urban area: a prospective epidemiologic study. Nephrol Dial Transplant. 1996;111542- 1546
Link to Article
Ifudu  ODawood  MHomel  PFriedman  EA Excess morbidity in patients starting uremia care without prior care by a nephrologist. Am J Kidney Dis. 1996;28841- 845
Link to Article
Jungers  PZingraff  JAlbouze  G  et al.  Late referral to maintenance dialysis: detrimental consequences. Nephrol Dial Transplant. 1993;81089- 1093
Innes  ARowe  PABurden  RPMorgan  AG Early deaths on renal replacement therapy: the need for early nephrological referral. Nephrol Dial Transplant. 1992;7467- 471
Sesso  RBelasco  AG Late diagnosis of chronic renal failure and mortality on maintenance dialysis. Nephrol Dial Transplant. 1996;112417- 2420
Link to Article
Stehman-Breen  COSherrard  DJGillen  DCaps  M Determinants of type and timing of initial permanent hemodialysis vascular access. Kidney Int. 2000;57639- 645
Link to Article
Schmidt  RJDomico  JRSorkin  MIHobbs  G Early referral and its impact on emergent first dialyses, health care costs, and outcome. Am J Kidney Dis. 1998;32278- 283
Link to Article
Perrone  RDMadias  NELevey  AS Serum creatinine as an index of renal function: new insights into old concepts. Clin Chem. 1992;381933- 1953
Mendelssohn  DCBarrett  BJBrownscombe  LM  et al.  Elevated levels of serum creatinine: recommendations for management and referral. CMAJ. 1999;161413- 417
Cockcroft  DWGault  MH Prediction of creatinine clearance from serum creatinine. Nephron. 1976;1631- 41
Link to Article
Coresh  JToto  RDKirk  KA  et al.  Creatinine clearance as a measure of GFR in screenees for the African-American Study of Kidney Disease and Hypertension pilot study. Am J Kidney Dis. 1998;3232- 42
Link to Article
Nicoll  SRSainsbury  RBailey  RRKing  AFrampton  CElliot  JR Assessment of creatinine clearance in healthy subjects over 65 years of age. Nephron. 1991;59621- 625
Link to Article
Sokoll  LJRussell  RMSadowski  JAMorrow  FD Establishment of creatinine clearance reference values for older women. Clin Chem. 1994;402276- 2281
DeSanto  NGCoppola  SAnastasio  P  et al.  Predicted creatinine clearance to assess glomerular filtration rate in chronic renal disease in humans. Am J Nephrol. 1991;11181- 185
Link to Article
Toto  RDKirk  KACoresh  J  et al.  Evaluation of serum creatinine for estimating glomerular filtration rate in African Americans with hypertensive nephrolsclerosis: results from the African-American Study of Kidney Disease and Hypertension (AASK) pilot study. J Am Soc Nephrol. 1997;8279- 287
Cochran  MSt John  A A comparison between estimates of GFR using [99mTc] DTPA clearance and the approximation of Cockcroft and Gault. Aust N Z J Med. 1993;23494- 497
Link to Article
Duncan  LHeathcote  JDjurdjev  OLevin  A Screening for renal disease using serum creatinine: who are we missing? Nephrol Dial Transplant. 2001;161042- 1046
Link to Article
Mendelssohn  DCKua  BTSinger  PA Referral for dialysis in Ontario. Arch Intern Med. 1995;1552473- 2478
Link to Article
Wilson  RGodwin  MSeguin  R  et al.  End-stage renal disease: factors affecting referral decisions by family physicians in Canada, the United States, and Britain. Am J Kidney Dis. 2001;3842- 48
Link to Article
Canadian Hypertension Recommendations Working Group, The 2001 Canadian hypertension recommendations: what's new and what's old but still important. The Canadian Hypertension Society Web site. Available at: http://www.chs.md. Accessed January 14, 2002.
Papaioannou  ARay  JGFerko  NCClarke  JACampbell  GAdachi  J Estimation of creatinine clearance in elderly persons in long-term care facilities. Am J Med. 2001;111569- 573
Link to Article
Khan  IHCatto  GREdward  NMacLeod  AM Chronic renal failure: factors influencing nephrology referral. QJM. 1994;87559- 564
Culleton  BFLarson  MGEvans  JC  et al.  Prevalence and correlates of elevated serum creatinine levels: the Framingham Heart Study. Arch Intern Med. 1999;1591785- 1790
Link to Article
Not Available, Statistics of renal replacement therapy: Canadian Organ Replacement Registry (CORR) annual report 2000. Canadian Institute for Health Information (CIHI) Web site. Available at: http://www.cihi.ca. Accessed September 25, 2001.
Not Available, US Renal Data System (USRDS) annual report 2000. USRDS Web site. Available at: http://www.usrds.org. Accessed September 25, 2001.
Kjellstrand  CM Age, sex, and race inequality in renal transplantation. Arch Intern Med. 1988;1481305- 1309
Link to Article
Bloembergen  WEMauger  EAWolfe  RAPort  FK Association of gender and access to cadaveric renal transplantation. Am J Kidney Dis. 1997;30733- 737
Link to Article
Kjellstrand  CMLogan  GM Racial, sexual and age inequalities in chronic dialysis. Nephron. 1987;45257- 263
Link to Article
Kausz  ATObrador  GTArora  PRuthazer  RLevey  ASPereira  BJG Late initiation of dialysis among women and ethnic minorities in the United States. J Am Soc Nephrol. 2000;112351- 2357
Drusano  GLMuncie  HLHoopes  JMDamron  DJWarren  JW Commonly used methods of estimating creatinine clearance are inadequate for elderly debilitated nursing home patients. J Am Geriatr Soc. 1988;36437- 441
Goldberg  THFinkelstein  MS Difficulties in estimating glomerular filtration rate in the elderly. Arch Intern Med. 1987;1471430- 1433
Link to Article

Figures

Place holder to copy figure label and caption
Figure 1.

Flowchart of the study design and results. C-G GFR indicates glomerular filtration rate estimated by the Cockcroft and Gault formula.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 2.

Comparison of serum creatinine level in the 55 men and women with severe renal failure (Cockcroft and Gault formula glomerular filtration rate [C-G GFR], ≤30 mL/min). Women had significantly lower mean serum creatinine values than men, despite a similar level of renal function. This is likely because of the smaller muscle mass of women compared with men, as suggested by the women's significantly lower mean weight. The asterisk indicates P<.005. To convert creatinine to milligrams per deciliter, divide by 88.4.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 3.

Investigation for causes and complications of severe renal failure (Cockcroft and Gault formula glomerular filtration rate, ≤30 mL/min) in the 40 nonreferred patients.

Graphic Jump Location

Tables

Table Graphic Jump LocationTable 2. Characteristics of Serum Creatinine as a Test for Renal Failure*

References

Schaubel  DEMorrison  HIDesmeules  MParsons  DAFenton  SS End-stage renal disease in Canada: prevalence projections to 2005. CMAJ. 1999;1601557- 1563
Collins  AXue  JMa  J Estimating the number of patients & Medicare costs for ESRD in the US to 2010 [online publication]. US Renal Data System Web site. Available at: http://www.usrds.org. Accessed September 25, 2001.
Giuseppe  PMario  SBarbara  PG  et al.  Elderly patients on dialysis: epidemiology of an epidemic. Nephrol Dial Transplant. 1996;11 (suppl 9) 26- 30
Link to Article
Jungers  PChauveau  PDeschamps-Latscha  B  et al.  Age and gender-related incidence of chronic renal failure in a French urban area: a prospective epidemiologic study. Nephrol Dial Transplant. 1996;111542- 1546
Link to Article
Ifudu  ODawood  MHomel  PFriedman  EA Excess morbidity in patients starting uremia care without prior care by a nephrologist. Am J Kidney Dis. 1996;28841- 845
Link to Article
Jungers  PZingraff  JAlbouze  G  et al.  Late referral to maintenance dialysis: detrimental consequences. Nephrol Dial Transplant. 1993;81089- 1093
Innes  ARowe  PABurden  RPMorgan  AG Early deaths on renal replacement therapy: the need for early nephrological referral. Nephrol Dial Transplant. 1992;7467- 471
Sesso  RBelasco  AG Late diagnosis of chronic renal failure and mortality on maintenance dialysis. Nephrol Dial Transplant. 1996;112417- 2420
Link to Article
Stehman-Breen  COSherrard  DJGillen  DCaps  M Determinants of type and timing of initial permanent hemodialysis vascular access. Kidney Int. 2000;57639- 645
Link to Article
Schmidt  RJDomico  JRSorkin  MIHobbs  G Early referral and its impact on emergent first dialyses, health care costs, and outcome. Am J Kidney Dis. 1998;32278- 283
Link to Article
Perrone  RDMadias  NELevey  AS Serum creatinine as an index of renal function: new insights into old concepts. Clin Chem. 1992;381933- 1953
Mendelssohn  DCBarrett  BJBrownscombe  LM  et al.  Elevated levels of serum creatinine: recommendations for management and referral. CMAJ. 1999;161413- 417
Cockcroft  DWGault  MH Prediction of creatinine clearance from serum creatinine. Nephron. 1976;1631- 41
Link to Article
Coresh  JToto  RDKirk  KA  et al.  Creatinine clearance as a measure of GFR in screenees for the African-American Study of Kidney Disease and Hypertension pilot study. Am J Kidney Dis. 1998;3232- 42
Link to Article
Nicoll  SRSainsbury  RBailey  RRKing  AFrampton  CElliot  JR Assessment of creatinine clearance in healthy subjects over 65 years of age. Nephron. 1991;59621- 625
Link to Article
Sokoll  LJRussell  RMSadowski  JAMorrow  FD Establishment of creatinine clearance reference values for older women. Clin Chem. 1994;402276- 2281
DeSanto  NGCoppola  SAnastasio  P  et al.  Predicted creatinine clearance to assess glomerular filtration rate in chronic renal disease in humans. Am J Nephrol. 1991;11181- 185
Link to Article
Toto  RDKirk  KACoresh  J  et al.  Evaluation of serum creatinine for estimating glomerular filtration rate in African Americans with hypertensive nephrolsclerosis: results from the African-American Study of Kidney Disease and Hypertension (AASK) pilot study. J Am Soc Nephrol. 1997;8279- 287
Cochran  MSt John  A A comparison between estimates of GFR using [99mTc] DTPA clearance and the approximation of Cockcroft and Gault. Aust N Z J Med. 1993;23494- 497
Link to Article
Duncan  LHeathcote  JDjurdjev  OLevin  A Screening for renal disease using serum creatinine: who are we missing? Nephrol Dial Transplant. 2001;161042- 1046
Link to Article
Mendelssohn  DCKua  BTSinger  PA Referral for dialysis in Ontario. Arch Intern Med. 1995;1552473- 2478
Link to Article
Wilson  RGodwin  MSeguin  R  et al.  End-stage renal disease: factors affecting referral decisions by family physicians in Canada, the United States, and Britain. Am J Kidney Dis. 2001;3842- 48
Link to Article
Canadian Hypertension Recommendations Working Group, The 2001 Canadian hypertension recommendations: what's new and what's old but still important. The Canadian Hypertension Society Web site. Available at: http://www.chs.md. Accessed January 14, 2002.
Papaioannou  ARay  JGFerko  NCClarke  JACampbell  GAdachi  J Estimation of creatinine clearance in elderly persons in long-term care facilities. Am J Med. 2001;111569- 573
Link to Article
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