Common Data Formatting Issues

QUESTION

As a test I'm regrouping some claims from the Medicare Inpatient SAF (LDS), and about 10% of the time, the results from the grouper do not match CMS's results. (Specifically, for around 1.2M claims, out of about 10M).

Some details:

• We're using the newest grouper executable.
• Mask version: 21 
• Claim Through Dates: 2003-Q4 through 2004-Q3

The return codes are almost always 0 but the results often do not match. Sometimes it's b/c we don't have exact ages (everyone under 65 is just listed as 65; we don't have better info than that in the LDS SAF).

The biggest example, for each quarters:

• Your grouper's result: 518
• CMS-assigned DRG: 527

We have checked & rechecked the input files, control files etc. Everything looks right. The grouper return codes are good, and totaling the PFLAGs and DFLAGs shows no inconsistencies.

ANSWER

We test against the CMS grouper all the time, so this is baffling.

To really see, we would need an example or two (scrubbed of identifiers, preferably). While it is possible that our grouper has a bug in it, we are pleased to report that this is exceedingly rare. Typically, the issues we see are data handling or trivial-seeming formatting issues:

• stripping leading zeroes from ICD9 codes
• leading whitespace on ICD9 codes
• non-contiguous ICD9 codes 
• discharge disposition coding

But why guess? Send us a few records--10? 100?--and we will see what we see.