Clinician reference tool — not medical advice. This is a clinical decision-aid intended for healthcare professionals: it gives deterministic suggestions to think with, not a diagnosis or a prescription. If you’re a patient, you’re welcome to look around — but please review anything here with your own doctor; it isn’t a substitute for personalized medical care.
← TestSelect

MELISA (memory lymphocyte immunostimulation assay) metal sensitivity test

Toxicology · specimen: blood

Rarely indicated

Also called: MELISA test, memory lymphocyte immunostimulation assay, lymphocyte transformation test, LTT, metal allergy blood test, metal sensitivity blood test, metal hypersensitivity blood test

Chart note

ND-recommended test reviewed: MELISA (lymphocyte transformation test for metal sensitivity).
Indications reviewed: suspected metal contact allergy, implant-related hypersensitivity; patch testing not yet done or not indicated today.
Not ordered. Rationale discussed: evidence for MELISA is mixed and patch testing remains the diagnostic standard. Ref: AAAAI Ask the Expert 2024.
Patient informed test available privately via ND. Patient given info page: https://labs.ajaxharwoodclinic.com/melisa/patient
Revisit if: implant-related symptoms persist despite a negative or inconclusive patch test.

Indicated when

  • Specialist-directed evaluation of suspected metal hypersensitivity related to a surgical implant (for example, a joint prosthesis) when patch testing is negative, inconclusive, or impractical, used alongside rather than instead of patch testing [1]

Not indicated when

  • As a first-line or stand-alone test for suspected contact allergy to metals such as nickel, cobalt, chromium, gold, or palladium: patch testing is the diagnostic standard [1]
  • General 'metal sensitivity' or 'metal toxicity' screening with no specific clinical question, such as implant-related symptoms or suspected contact dermatitis, behind it

Why not

The evidence here is genuinely mixed, and the AAAAI's own expert answer presents both sides. One comparison study (Cederbrant et al., discussed in [1]) found MELISA-type in-vitro assays had low specificity against gold, palladium, and nickel, with enough false positives that the authors concluded they were not useful for diagnosing contact allergy to those metals. A separate study (Vrbova et al., also discussed there) found high sensitivity and a correlation between MELISA results and symptom improvement after implant replacement. AAAAI's own conclusion is that patch testing remains the diagnostic standard 'for now,' given how few direct head-to-head comparisons exist between the two tests. A positive MELISA result on its own, without patch testing, should not be treated as a confirmed diagnosis.

Better first step

Refer to allergy/immunology or dermatology for patch testing, the validated standard for metal contact allergy. Where MELISA is used, it is a specialist-directed adjunct for a specific question, particularly implant-related hypersensitivity, not a general screening test.

Typical ND rationale

An ND may order MELISA reasoning that it is a blood test that avoids the skin-application and delayed-reading logistics of patch testing, and that it can screen broadly for reactivity to several metals at once in a patient with symptoms plausibly linked to dental or orthopedic metal exposure.

Where the ND is right

Genuine metal hypersensitivity exists and matters clinically, particularly around joint replacement surgery in a patient with unexplained implant-related symptoms, and there is real evidence that MELISA can correlate with clinical outcomes in that setting. Where the evidence doesn't support the approach is using MELISA as a stand-alone or first-line substitute for patch testing, given its inconsistent specificity across studies.

Ontario coverage & CONO orderability

OHIP status
unverified
MELISA does not appear by name in the 2026 Schedule of Benefits for Laboratory Services. It is a proprietary assay processed by a specific reference laboratory, and no Ontario community-lab billing code was identified for it this session. ND-ordered testing is patient-paid regardless (Reg. 552 s.22).
CONO orderable
Yes — CONO list #92
CONO list item 92, blood: 'Memory Lymphocyte Immuno-Stimulation Assay (MELISA Test).'

Linked conditions

Counselling script

“The evidence on MELISA is mixed: one study found it gives false alarms for some metals, another found it lines up with real symptoms after implant surgery. The standard test for metal allergy is still the skin patch test, so I'd start there, and if there's a specific implant-related question a patch test doesn't answer, we can talk about whether MELISA adds anything alongside a specialist opinion.”

Revisit if

  • Implant-related symptoms persist despite a negative or inconclusive patch test
  • A specialist referral for suspected metal hypersensitivity is being considered

References

  1. [1]American Academy of Allergy, Asthma & Immunology (Ask the Expert) (2024). Validity of the in-vitro test for metal (MELISA). linkPatch testing remains the diagnostic standard; one study found low specificity/false positives for MELISA-type assays against gold, palladium, nickel, another found high sensitivity and clinical correlation in implant patients; few head-to-head comparisons exist
Evidence notes

Only one source was verified this session (an AAAAI Ask-the-Expert answer); the two primary studies it discusses (Cederbrant et al. and Vrbova et al.) were not independently fetched and quote-verified, so their findings are reported here as AAAAI's characterization of them, not as directly verified primary sources. A dedicated AAAAI/EAACI position paper or systematic review specifically on MELISA/LTT for metal hypersensitivity was not located this session; flagged as a gap for a future pass.