Improved assessment of exercise training program effects on ischemia modified albumin serum levels by the use of 4 different laboratory methods

Background: Ischemia modified albumin (IMA), a marker of ischemic tissues is measured by the albumin cobalt binding (ACB) assay or the enzyme-linked immunosorbent assay (Elisa) method. Each method has its drawbacks. A transient increase in albumin levels at peak exercise due to hemoconcentration occurs, thus, the ratio IMA/Albumin may also be tested.

Aim: Evaluation of exercise training program effects on IMA levels by four different laboratory methods.

Methods: IMA serum level has been assessed using 4 different methods, pre & post exercise test (EXT), at baseline and at end of 12 weeks exercise program in 40 patients with a recent(<1 month) myocardial infarction (MI), PCI, or CABG (BL-EXT1 & 2 and EP-EXT1&2). The lab methods were: 1. ELISA, 2. ACB, 3. IMA-Elisa/Serum Albumin ratio, 4. ACB-IMA/Serum Albumin ratio, and for statistical analysis we used the Generalized Linear Mixed Model (GLMM).

Results: In 3 out of the 4 methods a beneficial program effect was found, EP- EXT2 IMA levels were lower than BL- EXT2 (ACB= p<.01; ACB/ALB=p<.01; IMA/ALB= p<.05). In post CABG patients, IMA-ELISA levels were higher only at BL, p<.05. When PCI was applied, only ACB/ALB ratio was lower, p<.001. Exercise duration and METS had similar effect, reducing only ACB/ALB ratio, p<.01 & p<.05 respectively. The only time invariant factor proved to have an effect on IMA was the EF%, detected only by the IMA-Elisa and by the IMA-Elisa/Albumin ratio, p<.05 & p<.05, respectively. EF% was negatively associated with these outcome differences, the lower the EF%, the higher was the IMA level. An EXT positive for of ischemia was associated only with ∆IMA-ACB levels (p<.05).

Conclusions: Several program effects could have been missed using only one or two IMA assays. The combined use of all four IMA laboratory methods may overcome potential drawbacks alleged to each method used separately.