A sensitive stain for aluminum in undecalcified cancellous bone

Aluminum is known to accumulate with age in bone and other tissues of humans, even in the absence of renal disease. Our study aimed to develop a histological staining method sufficiently sensitive to detect aluminum in plastic sections of undecalcified bone biopsies from healthy volunteers as well as from patients with renal and non-renal bone diseases. We used quantitative histomorphometry to measure the percentage of trabecular surface stained by aluminum and found that our new method was approximately 50% more sensitive for detecting aluminum than the Acid Solochrome Azurine (ASA) method which in turn was significantly more sensitive than the Aluminon method. Aluminon is widely used in pathology laboratories for diagnostic purposes despite concerns in the literature about Aluminon's limited sensitivity for aluminum. Our histomorphometric results showed that the newly developed method stained approximately 10% of the trabecular surface in bone sections from healthy controls, 38% from renal patients, 26% from patients with vitamin D deficiency, and 29% from patients with osteoporosis. Histomorphometric measurements of aluminum-stained trabecular surfaces in sections stained with ASA were consistent with those obtained in Walton-stained sections but proportionately lower. Moreover, the Walton and ASA methods stained aluminum at similar locations in adjacent bone sections. As the ASA and Walton methods are considerably more sensitive for bone aluminum than the Aluminon method, we recommend that either of them should be used in place of the Aluminon method for routine diagnostic purposes.