At the Clinical Institute of Clinical Chemistry and Biochemistry, in the Laboratory for Analysis of
Enzymes and Trace Elements we have introduced a modern technology for analysis of trace elements - Inductively Coupled Plasma Mass Spectrometry (ICP-MS). ICP-MS is a state-of-the-art technology for multi-elemental analysis of biological materials, characterised by great sensitivity,
specificity and repeatability. New technology has enabled the laboratory to expand the set of analysed trace elements and required the updating of existing reference intervals and the setting of new reference intervals.
To determine reliable reference intervals, we ensured a suitable adult Slovenian population by selecting pre-analytical and analytical procedures. The standard CLSI-C28-A3 guidelines were followed when performing the analysis protocol. In whole blood samples, 27 trace elements were determined by the dilution method in ammonium solution and ICP-MS technology: Li, Rb, Cs, Be,
Sr, Ba, Ga, Tl, Sn, Pb, As, Sb, Se, Ti, V, Cr, Mo, Mn, Co, Ni, Cu, Ag, Au, Zn, Cd, Hg and U. We determined reference intervals for trace elements in the blood of the adult Slovenian population: Lithium (Li) < 6.5 µg/l, Rubidium (Rb) 1597- 3529 µg/l, Caesium (Cs) < 6.0 µg/l, Beryllium (Be) < 0.271 µg/l, Strontium (Sr) < 21 µg/l, Barium (Ba) < 0.74 µg/l, Gallium (Ga) < 0.059 µg/l, Thallium (Tl) < 0.034 µg/l, Tin (Sn) < 0.62 µg/l, Lead (Pb) < 29 µg/l, Arsenic (As) < 1.64 µg/l, Antimony (Sb) not determined, Selenium (Se) 71-156 µg/l, Titanium (Ti) not determined, Vanadium (V) < 0.070 µg/l, Chromium (Cr) < 0.45 µg/l, Molybdenum (Mo) < 1.0 µg/l, Manganese (Mn) 4.2-14.1 µg/l, Cobalt (Co) < 0.33 µg/l, Nickel (Ni) < 0.25 µg/l, Copper (Cu) 508-1307 µg/l, Silver (Ag) < 0.232 µg/l, Gold (Au) < 0.008 µg/l, Zinc (Zn) 5944-7600 µg/l, Cadmium (Cd) < 1.49 µg/l, Mercury (Hg) < 4.6 µg/l and Uranium (U) < 0.019 µg/l. For reliable determination of Sb and Ti, we extended the standard routine protocol.
The results of the reference intervals of the Slovenian population were compared with available
global data sources and evaluated for matches and possible deviations. By comparison, we found that the differences between the reference intervals for trace elements between the compared populations were significantly influenced by geographical, economic and individual factors. We
found that for the interpretation of the Slovenian population it is unreliable to summarise and use
reference intervals of foreign populations With our research, we confirmed the extraordinary advantage and importance of determining our own reference intervals for trace elements, as only reliable reference intervals are the only correct approach in the interpretation of laboratory results.