Importance of creatinine analyses of urine when screening for abused drugs

Abstract

We report here a simple method involving urine creatine measurements for testing authenticity and reducing false-negative results in urine testing for drugs of abuse. Urinary creatinine in consecutive patient samples (n = 176) ranged between 0.1 and 31.9 mmol/L (mean 9.8 +/- SD 6.2) and the osmolality in these urines ranged between 49 and 1183 mOsm/kg (mean 595 +/- SD 276). With other consecutive samples in which creatinine was (arbitrarily chosen) less than 4.3 mmol/L (n = 85), the correlation with osmolality was lower. In 10 randomly selected urine samples from different patients, all "clean" for all drugs of abuse in initial immunological drug testing with approved methodology (in which creatinine was less than 4.3 mmol/L and osmolality was less than 200 mOsm/kg), five patients turned out to be drug positive after a simple concentration by volume. In a formerly heavy smoker of cannabis, the excretion of cannabinoids and creatinine was monitored for 93 days. The substances showed very good correlation throughout this period (r = 0.93, P less than 0.001), whereas simple measurements of cannabinoid concentrations would have falsely indicated several relapses of cannabis abuse. Urine samples used in drug-abuse testing should be tested for creatinine; if creatinine is less than 4.0 mmol/L, negative results for drugs may not be valid.

Interest of adjusting urine cannabinoids to creatinine level to monitor cannabis cessation therapy in heavy smokers with psychiatric disorders

“…The need to use a normalized cannabinoids excretion was highlighted two decades ago but is still not routinely applied in clinical laboratories. 9 A high frequency of relapse (45%), characterized by an increase in U CNC between two specimens, was observed and gave similar results to a previously published study that used contingency management. 4 Given the limited number of patients, significant pre- In order to build a predictive model of U CNC , only patients with at least three decreasing U CNC specimens were selected.…”

“…Thus, the use of a urinary creatinine-normalized cannabinoids (U CNC ) quantification may be useful to evaluate cannabis consumption and withdrawal more accurately, especially since increasing evidence suggests that U CNC is a better predictor of cannabis consumption relapse than cannabinoids without normalization. [9][10][11] Because of a lack of guidelines in U CNC interpretation, the main objective of this study was to develop a predictive model of U CNC decrease, to determine a creatinine-normalized threshold corresponding to 20 and 50 ng/mL cannabinoids cut-off values, and to provide new insights into the urinary elimination rate of cannabinoids for cannabis withdrawal in chronic and heavy cannabis users. • Creatinine normalization should be applied in toxicology instead of cannabinoids alone.…”

Creatinine in urine – a method comparison

“…As excessive or reduced fluid intake can substantially alter the concentration of substances in urine, the necessity of investigating the urine's dilution when measuring drugs of abuse (DOA) or performing ethyl glucuronide testing is widely known. [1,2] This is usually done by measuring creatinine, the internal anhydride of creatine. [3] Based on a normal range of creatinine excretion from 14 to 26 mg/kg per day for men and 11 to 20 mg/kg per day for women, the urine's creatinine concentration can vary massively, because the individual urinary creatinine output correlates better with muscle mass than with body weight.…”

“…[3] Based on a normal range of creatinine excretion from 14 to 26 mg/kg per day for men and 11 to 20 mg/kg per day for women, the urine's creatinine concentration can vary massively, because the individual urinary creatinine output correlates better with muscle mass than with body weight. [2] An obese person is thereby expected to have a lower urinary creatinine excretion than an athletic individual with the same or even lower body mass. [3] Nevertheless, the measured urinary creatinine concentration is frequently used to provide information about the dilution, independent of the individual body composition of the donor.…”

Urinary concentration of human chorionic gonadotrophin and its fragments as a prognostic marker in bladder cancer

“…The detection limit of the assay was 15 IU/L but a threshold of 25 IU/L was employed when samples were not corrected for urinary creatinine concentration [24,29]. Urinary creatinine was measured by the Jaffe method (alkalinepicrate reaction) [30]. Results were expressed as international units of hCG per litre and IU hCG per millimole of urinary creatinine.…”