Serum urea and creatinine in elderly population - effect of age on renal function tests

 

S S Bandebuche¹, S B Jagtap^2*, Yashoda Maladkar³

 

¹Associate Professor, ²Assistant Professor, ³II year MBBS, Department of Biochemistry, Smt. Kashibai Navale Medical College and General Hospital, Narhe, Pune-411041, Maharashtra, INDIA.

Email: santoshdoc007@gmail.com

 

Abstract               Background: Serum urea and serum creatinine is of great value in helping to ascertain the renal function in the clinical setting. Many patients have urea and creatinine levels which are above the normal adult reference ranges but only some have signs or symptoms of renal failure because renal handling of urea and creatinine  is also affected by the age of the patient. Material Methods: The study comprised of total 90 subjects which were divided into three age groups, 30-44 years, 45-59 years and 60-74 years to see the effect of aging on serum urea and creatinine. Results: Study confirmed that there is an age-related increase in serum urea levels (p < 0.001) and serum  creatinine ( p<0.001) Conclusion: It is essential for physicians to assess the renal function taking into account the advancement  age of the patients and  if require additional tests should be undertaken as supportive evidence  of renal disease.

Key Words: Creatinine, elderly, renal function, urea.

 

 

 

INTRODUCTION

The determination of serum urea and serum creatinine is of great value in helping to ascertain the renal function in the clinical setting. These are relatively low-cost tests, are available in any standard hospital laboratory and are relatively easy to run. They are essential in the assessment of renal function in the emergency department. Many patients have urea and creatinine levels which are above the normal adult reference ranges but only some have signs or symptoms of renal failure^1,2 because renal handling of urea and creatinine  is also affected by the age of the patient. Factors that compromise renal function in the elderly include a progressive, age-related fall in both renal blood flow and glomerular filtration rate and structural changes such as sclerosis of glomeruli, renal arteriosclerosis and interstitial inflammation or fibrosis.^3-6 World Health Organization (1963) has defined 'middle-age' as being 45-59 years, 'elderly' as being 60-74 years. So present study was planned to find out age wise variations in serum urea and creatinine levels in elderly population so that increase in the levels of these parameters should always to be considered with respect to advanced age of the patient while predicting the extent of renal failure.

 

MATERIAL AND METHODS

The present cross-sectional study was conducted on apparently healthy ambulatory  male subjects of age group 30 to 74 years , mainly the referral cases from different outpatient departments of the hospital presenting for routine check up. Institutional ethics approval was obtained.  The study was conducted on ambulant, normonatremic subjects who were in good health and did not have any illnesses or were taking drugs that influence water, electrolyte, or urea handling. Subjects having history of diabetes mellitus, renal disorders, liver disorders, hypertension or any other inflammatory condition were also excluded from the study. Variations in diet and muscle mass were not taken into consideration. After written informed consent, about 3 ml of fasting, venous blood sample was collected with all aseptic precautions in plain bulb for estimations of serum urea and creatinine. Serum urea and creatinine were analysed in CCL on EM360 autoanalyser. Serum urea was estimated by Urease-GLDH method [Reference range: 15-40mg/dl] and serum Creatinine was estimated by Jaffes method.[Reference range: 0.6-1.2 mg/dl]

Statistical Analysis: The variables were presented in terms of mean and standard deviation. The data were analyzed using student’s unpaired ‘t’ test. ‘p’ values <0.001 were considered significant.

 

OBSERVATION AND RESULTS

The study comprised of total 90 male subjects of age group 30 to 74 years, mainly the referral cases from different outpatient departments of the hospital presenting for routine check up. They were divided into three age groups, 30-44 years, 45-59 years and 60-74 years for statistical analysis to see the effect of age on serum urea and creatinine.

 

Table 1: Mean values of urea and creatinine in different age groups

		Age group
Analytes	30-44 yrs	45-59 yrs	60-74 yrs
Urea (mg/dl)	20.74±2.25	28.80±1.62	44.16±1.81
Creatinine (mg/dl)	0.76±0.09	0.93±0.07	1.37±0.09

 

Mean serum urea levels were significantly different (<0.001) between three age groups studied, in agreement with Ateig⁷, Ano et al.⁸, Fehrman-Ekholm and Skeppholm⁹ and Ahemad et al.¹⁰ Mean serum creatinine levels were significantly different (<0.001) between three age groups studied, in agreement with Jones et al.¹¹ who found differences in mean serum creatinine (SCM) levels at different ages and not in agreement with Feifeld¹², Fehrman⁹, Aono et al⁸ and Ahemad et al.¹⁰

DISCUSSION

Urea is the primary metabolite derived from dietary protein and tissue protein turnover. Creatinine is the product of muscle creatine metabolism. The amount of creatinine produced each day is related to muscle mass and does not vary greatly from day to day as it is endogenously produced and released into body.¹³ These two serum determinations are best viewed in concert, observing their absolute levels as well as their relation to one another. They are relatively low-cost tests, are available in any standard hospital laboratory and are relatively easy to run. They are essential in the assessment of renal function in the emergency department. In this study serum urea and creatinine were significantly increased with increasing age. Renal handling of urea and creatinine is also affected by the age of the patient. Factors that compromise renal function in the elderly include a progressive, age-related fall in both renal blood flow and glomerular filteration rate and structural changes such as sclerosis of glomeruli, renal arteriosclerosis and interstitial inflammation or fibrosis.^3-6. GFR declines gradually with age, even in people without kidney disease.  The decline of GFR with ageing is universally accompanied by changes in renal structure^14,15 The percentage of glomeruli affected by global glomerulosclerosis increases steadily with advancing age, even in the absence of any co-morbidity (such as hypertension), and the overall number of functioning nephrons also steadily declines with ageing¹⁶. Since age, sex and muscle mass affect serum urea and Creatinine concentrations, the results obtained in this study were not unexpected. However, despite the known effect of these variables on serum creatinine and urea, many laboratories still continue to use for elderly patients reference values derived from a younger population.  So if physicians observe value for urea and creatinine above adult reference range in healthy elderly, such values may be considered as usual value.

 

CONCLUSION

Elderly people are more at risk of some kidney and urinary tract diseases. But many patients have urea and creatinine levels which are above the normal adult reference ranges but only some have signs or symptoms of renal failure. Kidney diseases can be serious but early detection and proper treatment can increase the life of kidney. Though it can sometimes be difficult to distinguish the structural and functional changes of a kidney affected by a specific preventable or treatable disease from those of a kidney undergoing the inevitable consequences of aging, it is essential for physicians to assess the renal function taking into account the advancement of age of the patients and if require additional tests should be undertaken as supportive evidence of renal disease. Results of this study may highlight the importance of having separate. ranges for an elderly population.

 

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