There is a need to develop an inexpensive, minimally invasive technique to assess zinc status, which can be used in the field for population assessment and to measure the impact of interventions. We investigated the capability of a portable X-ray fluorescence (XRF) device for non-destructive analysis of zinc, using fingernail clippings obtained in the context of a community-based intervention study in 6-30 months old children in Burkina Faso.
Energy dispersive XRF was used to analyze nail clippings from 347 children, who were randomly assigned to one of four treatment groups for 48 weeks: 7 mg zinc/d (DPZ); 10mg zinc/d for 10d every 16wks (IPZ); 20mg zinc/d for 10d for diarrhea (TDZ); or no supplementation (NI). Nail clippings were obtained at the end of the study and measured using a radioisotope-based irradiator and a miniature photon spectrometer. Plasma was obtained from the same subjects for assessment of plasma zinc concentration (pZn).
The mean nail zinc levels for the DPZ and IPZ groups were 143.4 ± 3.6 and 142.5 ± 3.7µg/g respectively, statistically higher than both the TDZ (129.6 ± 2.6µg/g) and NI group (131.6 ± 2.8µg/g). Mean nail zinc levels for DPZ and IPZ were not statistically different from each other (p=0.836). Corresponding pZn increased significantly only in DPZ (72.9 ± 5.3mg/dL) compared to NI (67.3 ± 3.2mg/dL).
Zinc incorporated in nail protein may be a more stable indicator of zinc status than plasma. Zinc in fingernails is resistant to rapid fluctuations due to recent meals or infections. XRF could provide a useful field tool to guide intervention protocols.