Hydroxychloroquine, Serum
Use
Monitoring serum hydroxychloroquine concentrations helps assess patient compliance and adjust dosage in patients undergoing treatment with hydroxychloroquine for various conditions such as malaria, rheumatoid arthritis, and systemic lupus erythematosus (SLE). Accurate monitoring is crucial due to the drug's extensive tissue accumulation and potential toxicities, which include gastrointestinal disturbances, visual and hearing abnormalities, and neuromuscular excitability. It is also important because hydroxychloroquine has been evaluated in clinical trials for COVID-19 treatment and prophylaxis, although its efficacy and safety for these purposes remain unverified.
Special Instructions
Specimens must be collected immediately before the patient's next scheduled dose. Serum gel tubes are unacceptable as collection containers because hydroxychloroquine can bind to the gel, resulting in falsely low concentration readings. If not ordering electronically, complete and submit the Therapeutics Test Request form with the specimen.
Limitations
The test may be affected by improper specimen collection where serum gel tubes are used, leading to underestimation due to adsorption of the drug on the gel. Hydroxychloroquine has a very long terminal elimination half-life, necessitating consideration when interpreting serum levels. Clinicians should be aware of potential drug interactions and that toxic retinopathy is related to cumulative dose and duration of use.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 3684-8
- 3684-8
Result Turnaround Time
3-7 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.5 mL
Container
Red top (serum gel/SST are not acceptable); Submission in a plastic vial
Collection Instructions
Collect specimen immediately before the next scheduled dose. Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.
Storage Instructions
Refrigerated (preferred) for up to 28 days; Ambient for up to 21 days; Frozen for up to 28 days
Causes for Rejection
Use of serum gel tubes
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 21 days |
| Refrigerated | 28 days |
| Frozen | 28 days |