Overview
Urine drugs-of-abuse (UDS) panels use immunoassay to detect common drug classes: amphetamines, cannabinoids, cocaine metabolite, opiates, phencyclidine, benzodiazepines, and others per panel design.
Cross-reactivity causes false positives; sensitivity and detection windows cause false negatives, confirmation per SOP when indicated.
Classification
| Domain | Laboratory focus | Bench note |
|---|---|---|
| TDM | Narrow therapeutic index drugs | Trough/peak timing; institutional ranges |
| Digoxin | Cardioactive glycoside monitoring | Post-dose timing; DLIF interference awareness |
| Lithium | Mood stabilizer monitoring | Trough timing; NEVER lithium-heparin tubes |
| Valproate | Anticonvulsant monitoring | Free vs total when binding changes relevant |
| Phenytoin | Anticonvulsant monitoring | Protein binding; free/adjusted per institution |
| Toxicology screen | Immunoassay presumptive | Screen ≠ confirm; method-defined cutoffs |
| Ethanol | Volatile testing | Specimen integrity; clinical vs forensic context |
| Drugs of abuse | UDS immunoassay panels | Cross-reactivity; adulteration; confirm pathway |
| General rule | Laboratory framing only | Verify institutional ranges and SOP, no treatment |
Morphologic Features
Chemistry marker reference, morphologic cell identification is hematology, not TDM/toxicology chemistry framing.
Laboratory Characteristics
- Confirm method identity and units for TDM or toxicology assays
- Compare to method-specific therapeutic ranges or cutoffs (verify locally)
- Document draw timing relative to dose when available
- Watch tube type, adulteration, and interference per method SOP
Reference Intervals
Therapeutic ranges, critical limits, and immunoassay cutoffs are method- and institution-dependent. Verify institutional and method-specific intervals, do not invent absolute universal cutoffs as dogma.
| Parameter | Reporting note | Action |
|---|---|---|
| TDM agents | Method-specific therapeutic range | Verify local RI and critical limits |
| Digoxin | Timing post-dose; DLIF awareness | Verify local draw protocol and range |
| Lithium | Trough preferred; tube type critical | Never lithium-heparin; verify local range |
| Valproate | Total vs free when relevant | Verify binding context and local range |
| Phenytoin | Free/adjusted when institutionally used | Verify albumin context and local range |
| Toxicology screen | Presumptive language; method cutoffs | Confirm when clinically/lab indicated |
| Ethanol | Units and context vary | Verify institutional reporting and specimen SOP |
| UDS panels | Class-based immunoassay | Cross-reactivity; confirm per SOP |
| All | Institution-dependent | Escalate critical/toxic per local SOP, no treatment language |
Clinical and Laboratory Significance
UDS supports presumptive detection in workplace, clinical, and forensic contexts, reporting language and confirmation pathways vary.
Never skip confirmation when institutional SOP requires it for selected positives.
Differential Considerations
Therapeutic vs supratherapeutic vs toxic vs subtherapeutic vs preanalytical artifact vs screen cross-reactivity. Laboratory suggests; confirmation decides. No treatment recommendations.
Comparison Tables
TDM and toxicology laboratory framing
| Tool | Typical lab clue | Caveat |
|---|---|---|
| Trough draw | Many TDM agents | Verify agent-specific timing protocol |
| Peak draw | Selected agents | Verify local peak timing guidance |
| Steady state | Serial monitoring | Multiple half-lives before steady state |
| Immunoassay screen | Presumptive positive/negative | Confirmation when needed per SOP |
| Chromatography confirm | Definitive identification | Method-defined cutoffs and reporting |
| Critical limits | Institutional SOP | Never invent universal numeric dogma |
Classification Frameworks
TDM and toxicology interpretive frameworks vary by institution, always verify current institutional adoption and SOP version; do not invent absolute universal cutoffs as dogma. LabPedia provides laboratory framing only, no treatment recommendations.
Laboratory Notes
- Cross-reactivity common, confirm when SOP requires
- Adulteration checks per institutional protocol
- Cutoffs method-defined, verify locally
References
Authoritative textbooks, guidelines, and reviews supporting this reference entry. Verify reference intervals, critical limits, and reflex criteria against institutional protocols and current guideline editions.
Textbooks
- Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 8th ed. Elsevier; 2022.
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021.
- Bishop ML, Fody EP, Schoeff LE. Clinical Chemistry: Principles, Techniques, and Correlations. 9th ed. Jones & Bartlett; 2022.
CLSI and Professional Guidelines
- Therapeutic drug monitoring and toxicology laboratory testing guidance (verify current institutional protocol and any adopted TDM timing, therapeutic-range, and toxicology confirmation guidance).
- Clinical and Laboratory Standards Institute. Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Standard. CLSI document EP28-A3c. CLSI; 2010.
Frequently Asked Questions
Common questions about using this Drugs of Abuse . Chemistry markers and analytes Medical Laboratory Library reference in Medical Laboratory Science education.
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Drugs of Abuse . Chemistry is a Markers and Analytes entry in the LabPedia Medical Laboratory Library, written for Medical Laboratory Science reference lookup.
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