Background Recently, Medtronic notified customers that new correction factors should be used for their Slimline and Zinetics24 single-use, internal-standard pH catheters.
Aim and Methods We selected 24-h recordings of oesophageal and gastric pH with the Zinetics24 from our archives for five healthy subjects and for five gastro-oesophageal reflux disease subjects who were studied at baseline and again after 8 days of treatment with a proton-pump inhibitor. All pH values obtained with the old correction factors were rescaled using the new correction factors. Values for median pH, integrated acidity and time pH ≤ 4 were then calculated from pH values with old and new correction factors.
Results The new correction factors changed values for median pH, integrated acidity and time pH ≤ 4. Values for median pH and integrated acidity changed in a predictable, proportionate way, whereas values for time pH ≤ 4 did not.
Conclusions The new correction factors will not change the interpretation of previously published results with median pH or integrated acidity. In contrast, values for time ≤4 cannot be converted in an obvious way with the new correction factors. Instead, the raw pH data will need to be rescaled and values for time pH ≤ 4 recalculated using the rescaled pH data.