The abbreviation COC in drug testing panels is a standardized code that represents cocaine and its related metabolites. This code indicates that the biological specimen will be analyzed specifically for compounds resulting from the body processing the substance. Testing focuses not on the psychoactive compound itself, which rapidly leaves the body, but on the more stable byproducts created during metabolism. Understanding the target compounds and procedural cut-off levels illuminates how laboratories determine a positive result.
Identifying the Target Compound
The substance drug tests primarily look for is not the original compound, but a chemical byproduct called Benzoylecgonine. This compound is the major metabolite, formed when the liver processes the parent drug through hydrolysis. Since the parent drug is eliminated quickly, testing for it would only confirm very recent use.
Benzoylecgonine is significantly more stable in biological matrices, such as urine, and remains detectable for a much longer period. Its extended half-life, approximately 12 hours, makes it a reliable indicator of use. This stability is the reason Benzoylecgonine is selected as the primary target in most testing protocols.
Testing Methodology and Thresholds
Drug testing involves a two-tiered system to ensure accuracy and minimize false positives. The initial step is a presumptive screening test, often an immunoassay. This rapid, cost-effective method uses antibodies to detect metabolites, but it cannot definitively confirm the compound’s identity or concentration.
Any specimen yielding a presumptive positive result must undergo a confirmation test using a precise analytical technique, such as Gas Chromatography/Mass Spectrometry (GC/MS) or Liquid Chromatography/Mass Spectrometry (LC/MS). These methods separate the sample into its components, creating a unique molecular fingerprint. This confirms the exact identity and quantifies the specific concentration of the metabolite, distinguishing it from other compounds that might have caused a false positive.
A foundational concept is the “cut-off level,” which is the minimum concentration of the metabolite required to be reported as positive. These thresholds, expressed in nanograms per milliliter (ng/mL), are established by regulatory bodies to differentiate actual use from incidental exposure. For example, a common initial screening cut-off in urine is 300 ng/mL, with a confirmation cut-off typically set at 150 ng/mL. A negative result means the concentration was below this established threshold, not that the substance was entirely absent.
Duration of Detection Across Specimen Types
The length of time the metabolite remains detectable varies significantly depending on the biological specimen. Urine testing is the most frequently used method, offering a detection window that typically spans one to four days following a single use. For heavy or chronic users, the metabolite can accumulate, potentially extending the detection window to a week or longer.
Oral fluid, or saliva, testing provides a much shorter window of detection, generally capturing use within the past one to three days. This method is often employed to determine very recent use, as the parent compound and its metabolites appear quickly in the oral fluid. The shorter detection period makes saliva testing less effective for assessing long-term use patterns.
Hair follicle testing provides the longest detection window because the metabolite becomes incorporated into the hair shaft as it grows. A standard hair test analyzes a 1.5-inch sample, providing a retrospective look at the approximate 90 days prior to collection. While hair growth rates vary, this timeframe serves as a valuable tool for assessing a pattern of use over an extended period.
Variables Affecting Test Accuracy
Several factors can influence the accuracy of a drug test result. One complication is the risk of a false positive on the initial screening, which can occur due to cross-reactivity with certain medications or chemical compounds that have a similar molecular structure to the targeted metabolite. Although confirmation testing eliminates these false positives, initial screenings can sometimes be misleading.
Sample adulteration and dilution are attempts to manipulate a test result, and laboratories employ specific procedures to detect them. Adulteration involves adding a foreign substance, such as bleach, to interfere with the assay’s chemical reaction. Dilution involves excessively consuming fluids before a test, which lowers the metabolite concentration in the urine. Laboratories monitor for dilution by checking the specimen’s creatinine levels and specific gravity, which will be abnormally low in a diluted sample.
For hair testing, external contamination is a concern, where the hair may pick up the substance from the environment rather than through internal consumption. Laboratories mitigate this by washing the hair sample before analysis. The detection of specific metabolites within the hair shaft, rather than just the parent compound, is considered stronger evidence of systemic absorption.