Evaluation of a portable XRF device for in vivo quantification of lead in bone among a US population

Lead (Pb) concentration in bone is a reliable biomarker for cumulative Pb exposure and studying associated health outcomes. However, the standard K-shell fluorescence (KXRF) bone Pb measurement technology has limitations in large-scale population studies.

We compared measurements from a portable XRF device and a KXRF device.

We measured bone Pb concentrations in vivo using portable XRF and KXRF, each measured at the mid-tibia bone in 71 people, 38-95 years of age (mean ± SD = 63 ± 11 years) living in or near three Indiana communities, US; 10 participants were occupationally exposed. We estimated the correlation between bone Pb concentrations measured by both devices. We also examined the extent to which the detection limit (DL) of the portable XRF was influenced by scan time and overlying soft tissue thickness. Finally, we quantified the associations of estimated bone Pb concentration with age and age with soft tissue thickness.

The mean bone Pb concentration measured via portable XRF was 12.3 ± 16.7 mg Pb/kg dry bone. The uncertainty of a 3-minute (N = 60) in vivo portable XRF measurement ranged from 1.8 to 6.3 mg/kg, in the context of soft tissue thickness ranging from 2 to 6 mm. This uncertainty was reduced by a factor of 1.4 with 5-minute measurements (N = 11). Bone Pb measurements via portable XRF and KXRF were significantly correlated: r = 0.48 for all participants, and r = 0.73 among participants with soft tissue thickness < 6 mm (72% of the sample). Bone Pb concentrations were higher among participants who were older or were occupationally exposed to Pb. Soft tissue thickness decreased with age.

With its ease of use, portability, and comparable sensitivity with conventional KXRF systems, the portable XRF could be a valuable tool for non-invasive quantification of bone Pb in vivo, especially for people with thinner soft tissue.