April 13, 2016 | From the Lab Bench
Validities Tests, Part 1: How Creatinine Helps Detect Tampering
By Andrea Belec
Burlington Labs Laboratory Technical Manager
Every urine sample screened at Burlington Labs gets tested for four “validity” parameters: pH, general oxidant, specific gravity and creatinine. These values help us flag samples that may have been tampered with. In this post, we'll take a closer look at creatinine and specific gravity. For a deeper dive into pH and general oxidant, click here.
One of the most common strategies used by patients trying to “beat a drug test” is to drink large quantities of water and/or take diuretics before the test. Drugs are present in the urine in proportion to the urine concentration. When the urine is less concentrated (ie, diluted), there is also a lower concentration of drugs; so if a patient can dilute their urine enough, they can also bring the concentration of drugs below the lab’s cutoff for a positive result.
However, this strategy is easily flagged by looking at creatinine and specific gravity.
Creatinine is a by-product of the breakdown of creatine phosphate in the muscle, which occurs as part of normal biological function. Creatinine is naturally eliminated in the urine at a relatively stable rate, somewhere between 20 mg/dL (milligrams per deciliter) and 400 mg/dL. Less than 2% of people normally produce a urine sample with a creatinine level under 20 mg/dL. So when this result shows up, it’s a likely indicator that the patient is trying to beat the test.
Specific gravity measures the “urine density,” or the concentration of all chemical entities within the urine. If all chemicals are present in abnormally low concentrations – and not just the drugs being tested – then it’s likely a case of intentional dilution.
Sometimes a patient’s urine will show low creatinine if the person is incorporating more water into their diet as part of a healthy lifestyle and/or drinking beverages high in caffeine or other energy-boosting supplements like Monster or 5-Hour Energy. Caffeine and these supplements are diuretics and will draw out additional body water through urination. For these patients, we often recommend coming in first thing in the morning for their UA, since early eliminations tend to be more concentrated.
Questions about validities are some of our most common “FAQs,” and our scientists are always happy to speak with providers about test results.
This article appeared in the May/June edition of our newsletter, TheBuzz.