A technologist is asked to calculate a patients 24 hour crea

A technologist is asked to calculate a patient\'s 24 hour creatinine clearance. The urine sample is an aliquot from the total sample reported on the laboratory slip to be 800 mL. The plasma creatinine level is observed to be 14 mg/dl. The urine creatinine concentration is found to be 900 mg/dl. 1. What are the units of measure used for creatinine clearance? 2. What is the formula for the calculation of creatinine clearance, and what additional information is needed? The technologist assuming that the urine volume is a 24 hour sample calculates the creatinine clearance as 36 mL/min. That afternoon, a nephrologist calls the lab, questioning the accuracy of the result and asks for a reanalysis of the specimens. The technologists repeat the both the creatinine clearance analysis and the calculation and comes up with essentially the same results. The technologist then brings the problem to the laboratory’s clinical chemist. Together they review the patient’s demographics in the lab computer and find out that the patient is a 23-year-old, 225 pound 6’3” Caucasian male. 3. What is the usual volume of urine output for a healthy male? What is the usual amount of creatinine excreted in urine of such individuals? 4. Will the correction of the creatinine clearance for body surface give a more valid result? 5. What is the formula for correcting creatinine clearance for the body surface area? 6. What is the corrected value for creatinine clearance for this patient? 7. What is the reference range for serum creatinine and creatinine clearance? 8. What is most probably the cause of error? What should be done to correct the problem?

Solution

1). The units used to measure creatinine clearance is, \"ml/min.\" Both the inulin and creatinine are neither secreted, nor reabsorbed, so their concentration in the urine is used to measure the glomerular filtration rate.

2). Creatinine clearance, CrCl can be calculated by the below formula.

CrCl = [(140 - age) x ABW] / (Scr x 72)* (0.85 for females)

ABW = Actual body weight (ABW is used if it is less than IBW (ideal body weight))

Scr = serum creatinine