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 absorptio n. 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 stoves in patients with known excessive lead exposure. Serial measure ments revealed a reduction in bone lead that occurred over the years, during which there was an absence of continued exposure; this reductio n occurred more rapidly during chelation therapy. Sustained high bone lead levels following chelation therapy in two children were consisten t with elevated lead stores from prior pica. In a patient with renal f ailure, K-x-ray fluorescence demonstrated massive lead stores at a tim e when chelation testing was not possible. In other cases, bone lead l evels indicated the possible contribution of lead nephropathy to renal diseases of other etiologies. In individuals exposed to lead during h ome renovations, K-x-ray fluorescence provided reassurance that past e xposure did not result in elevated body lead stores decades later. In the occupational setting, K-x-ray fluorescence documented cumulative l ead stores in workers whose exposures varied in intensity and duration . The examples discussed here show how physicians can use K-x-ray fluo rescence to deal with practical questions of patient management. As th e test becomes more generally available, its safety, specificity, and simplicity should make it an important alternative to cumbersome chela tion tests and potentially misleading blood lead measurements.