Background: Plasma IGF- 1 was measured by Siemens Immulite 2000 since December 2003 at PathWest, Western Australia. A noticeable 40% shift in the IGF-1 levels was noted when Immulite 2000 was changed to Immulite 2000Xpi in August 2010. In December 2012, Siemens announced the shortage of IGF-1 reagent and PathWest adopted the assay on Diasorin Liaison analyser but continue with the reference intervals quoted by Siemens Immulite.
Aim: To assess the running medians of plasma IGF-1 medians on Liaison after the method change from Immulite.
Method: This is an observational and retrospective analysis of IGF-1 measurements in adults between January 2004 and June 2015 at PathWest QEII laboratory. Monthly medians and percentage of results above and below reference ranges were calculated.
Results: The monthly median of IGF-1 on Immulite prior to 2010 was between 130-150 ug/L. The 40% upward shift on the Immulite resulted in running median of 200-220 ug/L between 2010-2012. The monthly median on the Liaison since 2013 to 2015 was ~150 ug/L. Percentages of results above and below our quoted reference intervals on the Liaison have returned to similar proportions noted on the Immulite prior to 2010. We will also present results of patients having IGF-1 analysed on Immulite, Liaison and IDS-iSYS.
Conclusion: It has been reassuring that the monthly medians on the Liaison have been stable since introduction in our laboratory in 2013. The previous Immulite reference intervals have continued to apply well. The justification of using the pre-existing Immulite reference intervals at the time were from small number of comparison studies on Immulite (before the assay shift) and Liaison which showed good correlation. Clinicians need to be aware of the IGF-1 methodology that their laboratories are using and liaise with the biochemists if there is a discrepancy between the clinical scenario and the result.