(P06-09-26) Content Validation of the MagQuest Instrument to Support the Clinical Assessment of Magnesium Deficiency Risk

Objectives: Magnesium (Mg) status is notably difficult to assess, as the most common clinical measure — total serum magnesium (tMg) — reflects only ~1% of body stores, leaving subclinical deficiencies linked to hypertension and type 2 diabetes largely undetected. MagQuest, a computerized self-administered screening tool, was previously designed to identify Mg deficiency risk through dietary intake, medical history, and medication use. This project aimed to assess MagQuest's content validity.

Methods: Ten U.S.-based experts holding an MD or PhD with ≥10 years of relevant clinical experience and/or peer-reviewed publications on Mg participated in a two-round Delphi process to evaluate MagQuest using Lynn's (1986) content validation method. The panel represented nutrition, epidemiology, cardiology, gastroenterology, nephrology, mental health, and lab/pathology medicine, with six panelists having direct clinical experience. Experts rated each item (or item set) for relevance using a 4-point Likert scale; consensus was evaluated via item-level (I-CVI) and scale-level (S-CVI/Ave) Content Validity Indices. Qualitative feedback on clarity and comprehensiveness informed iterative item revision and addition.

Results: Of 18 MagQuest items/item sets evaluated in Round 1, 14 achieved consensus (I-CVI ≥ .80); expert feedback prompted the addition of 14 new items. The resulting 28-item instrument was evaluated in Round 2, with 21 items achieving acceptable content validity (I-CVI ≥ .88) and an overall S-CVI/Ave of .75, falling short of the ≥ .90 threshold. All seven items failing to reach consensus (I-CVI < .78) were medication items proposed by experts in Round 1; qualitative feedback indicated insufficient evidence to support their inclusion, particularly for newer agents.

Conclusions: Following removal of medication items that failed to meet consensus thresholds, MagQuest demonstrated acceptable content validity, with non-consensus results reflecting an evolving evidence base rather than a fundamental instrument weakness. MagQuest shows promise as a clinically practical screening tool for early identification of individuals at risk for suboptimal Mg status.

Funding Sources: No external funding