Exploratory Assessment of Leukocyte Adherence Inhibition Test and Tube Precipitation Responses to Hexavalent and Trivalent Chromium in Patients with Suspected Allergic Contact Dermatitis

Abstract

Background: Chromium compounds can elicit hypersensitivity reactions. No standardised laboratory assay is available to quantify the relative contributions of humoral and cellular mechanisms within an individual patient’s phenotype, apart from in vivo provocation testing. Aim: To evaluate the potential of the Tube Titration of Precipitins (TTP) and the Leukocyte Adherence Inhibition Test (LAIT) to characterise humoral and cellular immunoreactivity to hexavalent and trivalent chromium in patients clinically diagnosed with chromium-related allergic contact dermatitis. Study Design: This retrospective, single-centre study reviewed the medical records of two cohorts of patients with allergic contact dermatitis and suspected chromium hypersensitivity. The first cohort was evaluated using TTP, whereas the second cohort underwent ex vivo challenge testing monitored by LAIT using hexavalent and trivalent chromium preparations. Methodology: The recorded semi-quantitative serum TTP results for 1 mg/mL hexavalent and trivalent chromium solutions were grouped into ranges and displayed in cascade distribution charts to illustrate variability within the first cohort. The recorded leukocyte adherence inhibition (LAI) percentages from ex vivo challenges with 1 mg/mL hexavalent and trivalent chromium solutions were similarly grouped and displayed for the second cohort. Results: The paired t-test showed a small, statistically significant difference between trivalent and hexavalent LAIT responses (p < 0.001). Pearson’s correlation indicated a moderate positive association between trivalent and hexavalent LAIT responses, r(98) = 0.372, p < 0.001. The difference between trivalent and hexavalent chromium TTP responses was very small and not statistically significant (p = 0.898), and their correlation was also small and non-significant, r(98) = 0.00988, p = 0.922. The cascade charts showed broad distributions of TTP and LAI results. Conclusion: These preliminary findings indicate that TTP and LAIT responses to hexavalent and trivalent chromium may distinguish different degrees of humoral and cellular immunoreactivity in patients with allergic contact dermatitis. However, their clinical significance remains uncertain because the assays were not compared with an independent diagnostic reference standard, appropriate control groups, or relevant clinical outcomes. The findings should therefore be considered exploratory and hypothesis-generating rather than evidence supporting diagnostic or clinical application.