Clinical application of in vivo tibial K-XRF for monitoring lead stores.

We used in vivo tibial K-x-ray fluorescence for clinical evaluation of bone lead stores in 31 patients suspected of excessive lead absorption. Four clinical situations were examined: (1) postchelation therapy, (2) renal failure, (3) home exposure, and (4) occupational exposure. K-x-ray fluorescence assisted in determining the magnitude of body lead stores in patients with known excessive lead exposure. Serial measurements revealed a reduction in bone lead that occurred over the years, during which there was an absence of continued exposure; this reduction occurred more rapidly during chelation therapy. Sustained high bone lead levels following chelation therapy in two children were consistent with elevated lead stores from prior pica. In a patient with renal failure, K-x-ray fluorescence demonstrated massive lead stores at a time when chelation testing was not possible. In other cases, bone lead levels indicated the possible contribution of lead nephropathy to renal diseases of other etiologies. In individuals exposed to lead during home renovations, K-x-ray fluorescence provided reassurance that past exposure did not result in elevated body lead stores decades later. In the occupational setting, K-x-ray fluorescence documented cumulative lead stores in workers whose exposures varied in intensity and duration. The examples discussed here show how physicians can use K-x-ray fluorescence to deal with practical questions of patient management. As the test becomes more generally available, its safety, specificity, and simplicity should make it an important alternative to cumbersome chelation tests and potentially misleading blood lead measurements.