I have recently been introduced to a serum test called Metal-LTT (lymphocyte transformation test) which is said to measure immune cell reactivity (Type-IV delayed hypersensitivity) to metals. I have always read about the current patch testing to various metals to help define sensitivity. Could you provide any information or opinion on this test and any sensitivity or specificity? Thank You.


Thank you for your inquiry.

The test you referred to is not actually a serum test, but a whole blood test which measures lymphocyte reactivity upon exposure to metal. The test itself, that is, the lymphocyte transformation test, is a validated means of testing for delayed hypersensitivity, the type of hypersensitivity that results in contact dermatitis. How effective this is in detecting contact dermatitis to metal still remains somewhat undecided, but there is evidence in the literature that the test can detect delayed hypersensitivity to metals. This is of course important in dealing with metal implants.

We have actually answered a very similar question submitted to our website recently. I have copied the question and our response below. In addition, I have updated it with a link to the website of the company that performs this test should you wish to investigate it further, and other abstracts dealing with this issue.

In summary, the lymphocyte transformation test itself is a validated test for delayed hypersensitivity. It appears as if it can detect delayed hypersensitivity to metals, but its exact role, compared to patch testing for example, in detection of metal allergy has not been established to my knowledge.

Thank you again for your inquiry and we hope this response is helpful to you.

Orthopedic Analysis

How lymphocyte-mediated metal sensitivity affects orthopaedic implant performance remains poorly understood. Do patients with implants exhibit elevated lymphocyte reactivity to metals and is this reactivity more generalized or more implant-alloy specific? We investigated these questions by measuring lymphocyte responses to implant metals (Cr+3, Co+2, Ni+2 at 0.1 mM, and Ti+4 at 0.001 mM) in six subject groups: Group 1a = young controls, Group 1b = age matched controls, Group 2a = subjects with osteoarthritis (OA) and no history of metal sensitivity, Group 2b = OA subjects with history of metal sensitivity, Group 3a = total hip arthroplasty (THA) subjects with no to mild radiographic osteolysis, and Group 3b = THA subjects with moderate osteolysis. Lymphocyte proliferation, using Lymphocyte Transformation Testing (LTT), and cytokine release provided quantitative reactivity measurement, where a stimulation index of >2 indicated metal sensitivity. OA subjects with a history of metal sensitivity (Group 2b) were more metal reactive to Ni than any other group, as expected (66% incidence and Stimulation Index >20). However, THA subjects (Groups 3a & b) were >3 fold more reactive to Cr (p < 0.04), than were controls (Groups 1a & b) or OA subjects (Groups 2a & b). THA subjects with moderate vs mild osteolysis (Group 3b vs 3a) were more reactive to Co (43% vs 0% incidence). Only osteolytic THA subjects demonstrated increased cytokine responses with >two-fold (p <0.05) increases in soluble interferon-γ (IFN-γ) and interleukin-2 (IL-2) levels in response to Cr challenge. This elevated incidence and averaged level of lymphocyte reactivity supports a metal-specific adaptive immune response and suggests involvement in the pathogenesis of poor implant performance, e.g. aseptic osteolysis. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.(SOURCE Lymphocyte responses in patients with total hip arthroplasty,JOURNAL of ORTHOPEDIC RESEARCH 23(2), 384-391, 2005).

Contact Dermatitis. 2011 May;64(5):273-9. doi: 10.1111/j.1600-0536.2011.01886.x.
Metal sensitivity in patients with orthopaedic implants: a prospective study.
Frigerio E, Pigatto PD, Guzzi G, Altomare G.
Department of Technology for Health, Dermatological Clinic, IRCCS Galeazzi Hospital, University of Milan, Milan 20161, Italy.
Background: Sensitization to orthopaedic implant materials is an unpredictable event that might affect implant performance.
Objectives: In candidates for hip or knee joint prosthesis implantation, to evaluate preoperative assessments for identifying patients with metal sensitivity, to determine the percentage of patients who developed metal sensitivity at 1 year after prosthesis implantation, and to examine the clinical relevance of patch tests and lymphocyte transformation tests (LTT-MELISA®) for the evaluation of metal sensitization.
Patients and Methods: A total of 100 patients referred for total hip or total knee arthroplasty were assessed preoperatively and then at 1 year post-implantation by means of patch tests with the metals present in the implant alloys. In a pilot study, 20 patients also underwent both patch testing and a lymphocyte transformation test (LTT-MELISA®) for the same metals.
Results: Only 72 of 100 patients were patch tested both before and after surgery, and 12 of 20 also underwent LTT-MELISA® before and after surgery. Of 31/100 patients with an apparent history of nickel sensitivity determined during preoperative assessment of subjects, 12 tested negative on both tests, and 4 with a negative history of nickel sensitivity tested positive. One year post-implantation (72 patients), 5 patients who had initially tested negative for a metal allergy became positive for at least one or more metal constituents of the prosthesis on at least one or the other test.
Conclusions: Given the discrepancies between the information obtained while taking patient histories and test results, preoperative history-taking alone appears to be insufficient for identifying patients with metal sensitivity. Moreover, the increase in the percentage of patients who tested positive for metal sensitivity 1 year post-implantation suggests the possibility of prosthesis-induced sensitization. Therefore, objective determination of metal sensitivity at preoperative assessment should be considered in planning arthroplasty intervention, as it would help the surgeon in selecting the most appropriate prosthesis for the patient and could benefit implant performance.

Clin Exp Allergy. 2008 Sep;38(9):1468-75. doi: 10.1111/j.1365-2222.2008.02970.x. Epub 2008 Mar 31.
Detection of chromium allergy by cellular in vitro methods.
Lindemann M, Rietschel F, Zabel M, Grosse-Wilde H.
Institut für Immunologie, Universitätsklinikum Essen, Essen, Germany.
Background: The standard assay for the detection of chromium sensitization, the patch test, does not allow discrimination between patients with and without clinical symptoms of allergy.
Objective: The aim of this study was to prove whether cellular in vitro tests are predictive of chromium allergy.
Methods: Chromium-sensitized volunteers with and without clinically manifest allergy and non-sensitized healthy controls (n=37, 19, and 26, respectively) were analysed by cellular in vitro methods using tri- and hexavalent chromium (chromium chloride and potassium dichromate) as stimuli. The results were correlated with clinical and anamnestic data.
Results: Sensitized individuals with an allergy displayed significantly higher lymphocyte transformation test (LTT) responses than sensitized volunteers without allergy and controls (P<0.05 and P<0.01, respectively). 12.5 microg/mL of chromium chloride and 50 ng/mL of potassium dichromate were found to be optimal to discriminate between sensitized individuals with and without allergy. Combining the results of chromium chloride and potassium dichromate LTT, a positive reaction to at least one of the stimuli was highly predictive of allergy [sensitization with vs. without allergy: Odds ratio (OR)=6.4, P=0.004; sensitization with allergy vs. controls: OR=11.5, P<0.0001]. On the contrary, IFN-gamma, IL-2, IL-4, IL-10, and IL-12 production to the ELISpot, patch test results, sensitization against other metals, and atopy score did not significantly discriminate between sensitization with and without allergy. However, IFN-gamma responses towards chromium chloride were significantly correlated with the strength of patch test reactivity (r=0.49, P=0.002). By IFN-gamma ELISpot, the average precursor cell frequency reactive to trivalent chromium could be defined as 26, 15, and 11 : 10(6) in volunteers with sensitization and allergy, with sensitization without allergy, and controls, respectively.
Conclusions: In contrast to the patch test, the LTT appears to be a method that is predictive of chromium allergy.

Question posted to Ask the Expert website 4/25/2012:
Do you feel that Lympocyte Transformation Tests are reasonable diagnostic alternates to patch testing for metal allergy? e.g. MELISA Foundation, etc. I realize that the data is limited but at least one reference indicates possible value for these modalities.

Klinik und Poliklinik für Dermatologie und Allergologie der Ludwig-Maximilians-Universität,
München, Germany.
There are very few reports on hypersensitivity reactions in association with titaniumbased materials so that the existence of allergy to titanium is still put in question. We report on a patient in whom impaired fracture healing and eczema localized to the perioperative area developed upon titanium-based osteosynthesis. Patch testing gave no reactions to titanium nor to nickel, chromium, or cobalt. However, in the lymphocyte transformation test, the patient's lymphocytes showed markedly enhanced proliferation in vitro totitanium. After removal of the titanium material, fracture healing was achieved and the eczema cleared. Parallel to this, in vitro hyperreactivity to titanium disappeared. Although contact allergic reactions to titanium have been very rarely reported, these findings support a diagnosis of titanium allergy in our patient.

I think that there is credible evidence in the literature to indicate that delayed hypersensitivity testing to metals can be a useful test in detecting the presence of contact allergy. I am sending you a link (copied below) to a study employing delayed hypersensitivity testing to detect metal allergy. In addition, there is evidence in the dermatologic literature (1) indicating that lymphocyte transformation testing may be coming of age in terms of its usefulness to detect contact allergy not only to metals, but to other substances.

As with all tests, there are false-positives and false-negatives, and the diagnosis of contact allergy remains a clinical diagnosis in which tests are used to add additional evidence of its existence to a specific agent. Thus interpreting these tests is much like interpreting the immediate hypersensitivity skin tests and tests for serum-specific IgE. The reference to which I sent the link will give you some perspective on false-positive and false-negative tests using delayed hypersensitivity testing.

1. Basketter D and Menne T. Lymphocyte transformation tests in patients with allergic contact dermatitis. Contact Dermatitis 2005; 53:1.

Phil Lieberman, M.D.

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