In patients with severe hypoglobulinemia, which lab result might be misleading?

In cases of severe hypoglobulinemia, total serum calcium levels may be misleading due to the way calcium exists in the bloodstream. Calcium in the body exists in two forms: bound to proteins (mainly albumin) and in its free ionized form. When there is a deficiency of protein, like in severe hypoglobulinemia, the levels of total calcium can appear lower than normal because the protein-bound fraction is also decreased. However, the ionized calcium—the physiologically active form—may remain normal or only slightly altered. Consequently, measuring total calcium without accounting for protein levels can result in an inaccurate clinical picture, as it does not reflect true calcium metabolism or balance in the body.

In clinical practice, it is important to consider the patient's serum albumin levels alongside total calcium measurements to ascertain whether calcium status is genuinely low or simply a function of low protein levels. Thus, total calcium levels can become an unreliable indicator of calcium homeostasis in patients suffering from conditions like severe hypoglobulinemia.