Oral DMSA Urine Challenge Testing Should Not Be Performed
The oral DMSA "challenge" or "provocation" test is not recommended for clinical use, as there is no validated protocol, no established reference ranges for provoked urine samples in healthy subjects, no reliable evidence supporting diagnostic value, and potential for patient harm. 1
Why This Test Is Not Recommended
Lack of Standardization and Validation
- No standard, validated challenge test protocol exists despite various practitioners using different approaches 1
- Dosing regimens vary widely without consensus (ranging from 10-30 mg/kg/day in therapeutic contexts) 2, 3
- Urine collection procedures are inconsistent across different testing protocols 1
- Results are compared to inappropriate reference ranges that do not account for post-chelator administration 1
Fundamental Scientific Problems
- Human volunteer studies demonstrate that metals like mercury are detected in urine of most people even without known exposure or chelator administration 1
- Urinary metal excretion rises after chelator administration regardless of exposure history and in an unpredictable fashion 1
- Challenge testing fails to reveal a "body burden" of metals from remote exposure 1
- The test cannot distinguish between recent exposure requiring treatment versus background levels 1
Misleading Interpretation Issues
- Creatinine correction of urine obtained within hours of chelator administration is methodologically flawed 1
- Inter- and intra-individual variation in response to DMSA is substantial, making interpretation unreliable 3
- Blood lead concentration correlates with chelatable lead differently for DMSA versus EDTA, suggesting differential access to storage sites rather than total body burden 4
If DMSA Must Be Used Therapeutically (Not for "Challenge Testing")
Established Therapeutic Dosing for Lead Poisoning
When DMSA is used for actual treatment of confirmed lead poisoning (not diagnostic testing):
- Standard dose: 30 mg/kg/day orally, which is more effective than 10 or 20 mg/kg/day 2
- Typically divided into multiple daily doses 2
- Initial treatment courses of 5 days, with treatment-free periods of at least 1 week between courses to allow lead redistribution 2
- Maximum urine lead enhancement typically occurs with the first dose 2
Monitoring During Therapeutic Use
- Transient ALT elevation occurs in up to 60% of patients but rarely causes clinical sequelae 2
- Skin reactions occur in approximately 6% of treated patients and can occasionally be severe 2, 3
- Monitor for increased copper and zinc excretion, though not typically clinically significant 2, 3
Critical Distinction
The therapeutic use of DMSA for confirmed metal poisoning is entirely different from using it as a diagnostic "challenge test." The former treats documented toxicity; the latter attempts to diagnose exposure through an unvalidated methodology that professional organizations explicitly recommend against 1.
Professional Recommendations
Multiple professional and government organizations recommend against provoked urine testing for metals 1. The evidence consistently shows these tests lack diagnostic validity and may lead to unnecessary chelation therapy with associated risks.