Predictor measurement reliability

I am looking at the prognostic/diagnostic value of an inflammatory biomarker (SAA) for diagnosing/predicting neonatal sepsis. There is individual patient data available from a number of authors but the methods for measuring SAA include laboratory and point of care methods which are not concordant at all levels. Is there a way to combine these measurements even if they are not using the same methodology?

Could you use the simple regression equation to harmonize measurements?

I found this :