Generally, findings from an aluminum level blood test are unreliable, as most of the body's stores are bound in bone and tissue and are not reflected in the serum value. A deferoxamine infusion test can be performed but may take more than 48 hours to yield a result (see Medical Care). Deferoxamine liberates aluminum from tissues by chelating it and leads to an increased serum level compared with one taken prior to infusion. The combination of a baseline immunoreactive parathyroid hormone level of less than 200 mEq/mL and a change in serum aluminum value of 200 ng/mL after deferoxamine is 90% specific and has a positive predictive value of 85% for aluminum toxicity.
Aluminum excess has a direct effect on hematopoiesis and has been shown to induce anemia. Findings on peripheral smears in patients with aluminum toxicity include microcytic anemia (hypochromic, normochromic), anisocytosis, poikilocytosis, chromophilic cells, and basophilic stippling. Note that these are the same findings observed in patients with lead poisoning. Aluminum can also be found in bone marrow macrophages.
In radiographs, Looser zones (ie, lines of radiolucency parallel to the plane of growth in long bones) may be observed in severe cases, although they are more common with other causes of adult osteomalacia. Pathological fractures may also be observed. Bone scintigraphy shows a characteristic pattern in aluminum toxicity.
Bone biopsy from the iliac crest is frequently performed to determine the etiology of bone disease in patients on dialysis because renal osteodystrophy can be multifactorial (eg, osteomalacia, uremic bone disease, hyperparathyroidism, aluminum deposition). Histochemical staining for aluminum and determination of osteoid volume, bone turnover rate, and osteoblast/clast cell count are some of the methods used for subtyping the bone disease.
Very few procedures are involved in the diagnosis of aluminum-related illness. Bone marrow biopsy is performed to distinguish between aluminum osteodystrophy and other causes of osteomalacia.
Histologic findings in aluminum-related osteomalacia reflect the decrease in mineralization of newly formed bone matrix.
An increase in the surface covered by osteoid occurs, as does an increase in the osteoid seams.
Osteoid volume and thickness also increase.
In histologic sections stained with eosin, the areas of greater mineralization tend to appear violet or blue, whereas the osteoid seams appear pink.
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