You can either expand the summary data, or use PROC FREQ to summarize the observed data. For this situation, I'd suggest summarizing the new data by running PROC FREQ on the new observations; see the 2nd example of http://blogs.sas.com/content/iml/2011/09/19/count-the-number-of-missing-values-for-each-variable/ Then you can use a short DATA step to consolidate the old summary and the new summary, and use PROC FREQ with a WEIGHT statement to take the frequencies into account when you do the chi-square test.
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