COMPARISON BETWEEN CREATININE AND CISTATIN C FOR RENAL FUNCTION ASSESSMENT

Abstract

THE ASSESSMENT OF RENAL FUNCTION LEVEL IS THE KEY TO THE DIAGNOSIS, MONITORING AND MANAGEMENT OF KIDNEY DISEASES, AS WELL AS TO APPROPRIATE CALCULATION OF DOSES OF DRUGS THAT ARE EXCRETED BY THE KIDNEYS. GLOMERULAR FILTRATION RATE (GFR), WHICH IS DEFINED AS CLEARANCE OF A SUBSTANCE PRESENT IN PLASMA, METABOLIZED ONLY BY THE KIDNEYS AND FREELY FILTERED BY THE GLOMERULI, IS AN INDICATOR OF RENAL FUNCTION IN HEALTHY AND SICK INDIVIDUALS. CYSTATIN C IS A CYSTEINE �€‹�€‹PROTEINASE INHIBITORY PROTEIN SYNTHESIZED BY ALL NUCLEATED CELLS AT A CONSTANT RATE OF PRODUCTION AND CAN BE FOUND IN VARIOUS BIOLOGICAL FLUIDS. THE AIM OF THIS STUDY WAS TO COMPARE THE ADVANTAGES AND DISADVANTAGES BETWEEN CREATININE AND CYSTATIN C TESTS FOR RENAL FUNCTION EVALUATION. THIS IS A BIBLIOGRAPHIC REVIEW OF SCIENTIFIC ARTICLES OBTAINED IN THE GOOGLE ACADEMIC, SCIELO, PUBMED, DATABASES PUBLISHED BETWEEN 2000 AND 2016, USING AS DESCRIPTORS "CYSTATIN C", "CREATININE". THIS BIBLIOGRAPHICAL REVIEW WAS ELABORATED THROUGH 10 ARTICLES, OF WHICH 7 WERE USED IN THE ACCOMPLISHMENT OF THE SAME ONE. CREATININE IS NOT AFFECTED BY DIET OR PROTEIN CATABOLISM AND INCREASES LITTLE IN CASES OF DEHYDRATION OR HEART FAILURE, EXCEPT IN SEVERE CASES. HOWEVER, IT INCREASES SIGNIFICANTLY AND RAPIDLY IN RENAL FAILURE. CREATININE DOSAGE IS A VERY SPECIFIC MARKER OF RENAL DAMAGE, BUT IT IS A POORLY SENSITIVE MARKER TO ESTIMATE GLOMERULAR FILTRATION, ESPECIALLY IN THE EARLY STAGES OF RENAL FAILURE. ACCORDING TO GABRIEL, ET.AL., THE ACCURACY OF CREATININE CAN BE ALTERED BY SEVERAL FACTORS, SINCE THE SERUM CONCENTRATION IS DIRECTLY RELATED TO MUSCLE MASS AND IS INFLUENCED BY AGE AND SEX. THIS ALLOWS INTRA AND INTERINDIVIDUAL VARIATION, WHICH JUSTIFIES A HIGHER PLASMA LEVEL IN MEN THAN IN WOMEN AND IN ADULTS THAN IN CHILDREN. CYSTATIN C HAS BEEN SHOWN TO BE AN ADEQUATE TEST TO EVALUATE THE GLOMERULAR FILTRATION RATE, PRESENTING CHARACTERISTICS OF AN IDEAL ENDOGENOUS MARKER, BEING EVEN HIGHER THAN CREATININE. IT PRESENTS AS ADVANTAGE THE CONSTANT SERUM CONCENTRATION REGARDLESS OF SEX, AGE, MUSCLE MASS AND BODY WEIGHT. THEREFORE, NO DIFFERENCES WERE REPORTED BETWEEN THE VALUES �€‹�€‹REFERRING TO THE FEMALE AND THE MALE. IN CHILDREN, THE REFERENCE VALUE IS THE SAME AS FOR ADULTS AND STABILIZES IN THE SECOND YEAR OF THE CHILD'S LIFE. ANOTHER ADVANTAGE OF CYSTATIN C IS THE DISPENSING OF URINE COLLECTION FOR 24 HOURS FOR CLEARENCE. SOME AUTHORS HAVE SUGGESTED THAT CYSTATIN C PROVIDES A BETTER ESTIMATE OF GFR IN DIABETIC PATIENTS. DUE TO ITS HIGH COST, CYSTATIN C IS ALMOST UNUSED FOR MOST SERVICES, REPRESENTING APPROXIMATELY EIGHT TIMES THE VALUE OF CREATININE. HOWEVER, DESPITE THIS PRICE DISADVANTAGE, IT PRESENTS MORE SPECIFIC RESULTS WHEN IT COMES TO THE ASSESSMENT OF GLOMERULAR FILTRATION, WHICH DIFFERS FROM CREATININE WHICH IS A CHARACTERISTIC MARKER OF RENAL INJURY. THEREFORE, IT WAS CONCLUDED THAT THE TRAINED PROFESSIONAL SHOULD EVALUATE THE COST BENEFIT OF THE TWO EXAMS, BASED ON THE PARTICULAR CHARACTERISTICS OF EACH PATIENT.