I am performing analyses for a study concerning patients with delirium. I am using crosstab to obtain OR and RR for risk factors. For several risk factors, SPSS has calculated OR and RR, which do not seem to align with the remainder of the analysis. I cross-checked this using Excel to calculate OR and RR for some factors Excel and SPSS agree, and in other factors, they are in disagreement. There are a few factors where dividing 1 by the OR obtained in SPSS will be equivalent to the OR in Excel (ex: 1/.117 = 8.54), but this is not universal. Why is this disagreement occurring? and How do I know which one (Excel or SPSS) is correct or when to do the additional division?

Without a concrete example - the data and your results showing the discrepancy - it may be hard to answer.