Magnesium matters: unveiling hidden risks in kidney transplant patients through total and ionized magnesium profiling.

BACKGROUND

In kidney transplant (KT) patients, magnesium (Mg) deficiency is widespread. It is often encountered early after KT, may persist longer, and is frequently promoted by calcineurin inhibitors (CNIs) and tubular leakage. Studies demonstrated an association between post-KT hypomagnesemia and allograft dysfunction. The concentration of the active form, the ionized Mg (iMg), is not measured clinically, and total Mg (tMg) and iMg correlations are conflicting. We assess the cross-sectional prevalence of hypomagnesemia in KT patients. The correlation of demographic and anthropometric parameters was also studied.

METHODS

A prospective, single-center analysis of KT patients was conducted at the University Hospital of Bern, Switzerland (March 2023-August 2023). Blood samples were collected at least twice for the majority of patients. tMg has been quantified from a plasma sample at the Clinical Chemistry Department of the University Hospital of Bern. The PRIME ES analyzer (Nova Biomedical, USA) provided results for iMg. The following co-variables were considered: age, comorbidities, kidney disease, KT history, estimated glomerular filtration rate (eGFR), and treatment (including Mg supplementation and immunosuppression).

RESULTS

A total of 208 measurements in 104 patients were performed [once in 9/104 patients (8.7%), twice in 86/104 (82.7%), and three times in 9/104 (8.7%)]. Compared to that in healthy volunteers (51 measurements in 51 participants), mean iMg was significantly lower in KT patients {KT: 0.46 mmol/L [interquartile range (IQR): 0.40-0.50], volunteers: 0.57 mmol/L (IQR 0.54-0.61), p < 0.01}. Overall, iMg and tMg showed strong category agreement (r = 0.93, p < 0.01). In linear regression, low iMg correlated with CNI exposure. For 110/208 measurements (52.9%), a reduced iMg (cutoff: 0.42 mmol/L) was shown. In 58/208 (27.9%), both values were reduced, and 52/208 (25%) had isolated reduced iMg. In principal component analysis, patients with isolated low iMg clustered with patients with low iMg and tMg.

CONCLUSION

iMg and tMg were strongly correlated. A substantial proportion of patients show isolated low iMg. Currently, it is unclear if these patients suffer from Mg deficiency.