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Creatinine (CREA)
Creatinine is a degradation product of creatine in muscle metabolism. The daily production of
creatinine is fairly constant and not influenced markedly by age, diet, exercise, or catabolism.
Creatinine is eliminated from the body by glomerular filtration and tubular secretion in the kidneys.
Principal Reasons for Performing the Test
As an indicator of renal disease and/or an index of glomerular filtration rate.
Most Common Abnormality Indicated by the Test
Increased creatinine—prerenal, postrenal, and renal azotemia.
Sample Type and Precautions
Remove plasma or serum promptly from the cells or clot. If plasma is being collected, use only
lithium heparinized samples.
Interfering substances, such as creatine, in a sample can affect the analyzer’s ability to accurately
provide creatinine results. When the analyzer detects such an interfering substance, dilution of the
sample may be required to obtain an accurate creatinine value.
Complementary Tests
A complete urinalysis with a refractometry specific gravity measurement is essential for proper
interpretation of increases in creatinine. Creatinine determinations should usually be performed
in conjunction with measurements of BUN, inorganic phosphate, total protein, and albumin. A
complete blood count (CBC) can sometimes demonstrate changes such as nonregenerative
anemia with chronic renal failure.
Reaction Sequence
Fructosamine (FRU)
Fructosamine is glycated albumin or other proteins. Its concentration is related to blood glucose
concentration during the preceding 2 to 3 weeks.
Principal Reason for Performing the Test
Measurement of fructosamine concentration as part of the routine evaluation of a diabetic patient
undergoing therapy. It provides information about the status of glycemic control during the 2–3
weeks prior to evaluation. In cats, fructosamine concentrations can be measured to identify
if a stress response or diabetes mellitus is the reason for high blood glucose concentrations.
In addition, during management of diabetes in both canine and feline patients, fructosamine
concentration is used to clarify discrepancies between the history and physical examination
findings and serial blood glucose concentration measurements and it is also used to assess the
effectiveness of therapy.
Appendices
