Qualitative vs. Quantitative Drug Testing
Sometimes billing for drug testing can become pretty confusing. Here are some basics:
Drug testing codes in the Pathology and Laboratory chapter of the CPT® code book are defined as either qualitative or quantitative. A qualitative test tells you if a particular substance (analyte) is present in the specimen. A quantitative test tells you how much (the quantity) of an analyte is present.
After the presence of an analyte has been established (which may involve a second, confirmatory test), the amount of the analyte present in the sample then may be measured. For example, you could test for the presence of alcohol in the blood (qualitative), and/or may test for the actual blood alcohol level (quantitative).
CPT® lists the drugs/drug classes that may be assayed under the “Drug Testing” subhead. These include alcohols, amphetamines, barbiturates, methadones, opiates, and others. As described above, if the presence of a drug/drug class is confirmed by qualitative screening, a quantitative screen may follow.
The most common mechanism by which drug screens are performed is known as chromatography, which involves passing a mixture that’s dissolved in a mobile phase through to a stationary phase. This process isolates different molecules by type, after which each type can identified and measured.
When chromatography is used to identify multiple drug classes simultaneously, the appropriate code is 80100 Drug screen, qualitative; multiple drug classes chromatographic method, each procedure. Per CPT® instructions, count each combination of stationary and mobile phase as one procedure. “For example,” CPT® guidelines continue, “if the detection of three drugs by chromatography requires one stationary phase with three mobile phases, use 80100 three times [once for each of the mobile phases]. However, if multiple drugs can be detected using a single analysis (e.g., one stationary phase with one mobile phase), use 80100 only once.”
Codes for quantitative testing are more specific to the type of drug being measured. For example, quantitative testing for amphetamines is reported 82145 Amphetamine or methamphetamine, while the same testing for phencyclidine is reported 83992 Phencyclidine (PCP). You can find a quick and easy reference guide for drug testing codes—both quantitative and qualitative—by drug type, in the Pathology and Laboratory chapter Table of Contents.