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Accepting Zero Values

By:  Paul Meehan, DCRI

 In the 2.35 version of the data specifications, the fields Perfusion Time (PerfusTm), Cross Clamp Time (XClampTm), and Postop Vent Hours (VentHrs) all allowed value ranges starting with zero.  In the 2.41 version of the data specifications, these fields were changed to make the valid data ranges start at one and did not allow values of zero. 

Also in the 2.41 specifications, the fields Initial ICU Hours (ICUInHrs), Total Hrs ICU (TotHrICU), and Initial Hours Ventilated (VentHrsI) were added as new fields, all of which had valid data ranges starting with one and did not allow values of zero.

At the overwhelming request of the data managers, it is now permissible to collect zero values in these fields.  The purpose of the change was to help keep these fields from showing up as “missing” in Data Quality Reports and data completeness checks.  These fields can now also be collected in decimal format and not just whole numbers.  A message describing these changes was sent to all of the certified vendors in February of 2003.  These are optional changes for the vendors as well as the sites at this time.  It is left to the vendors to decide if they have the time and resources available to make the necessary changes to their software and get the upgrades installed for their users.  When the 2.5x version of the specifications is released at the end of 2003, it will include changes specifically designed to handle these issues.

If a participant’s software is upgraded to include these changes, it is up to the participant to decide whether past records collected in 2.41 format need to be updated to insert zeros for missing values.

When the analysis is done on these fields at the data warehouse, averages will be calculated using the number of records with values greater than zero as a denominator.  In this way, whether or not past records are updated will have no affect on the analysis results.  Participants will need to make similar considerations when they are analyzing their own data.  Participants must to be careful not to include any zero values in any analysis they do at their own site as they can greatly skew the resulting values.

The fields Additional ICU Hrs (ICUAdHrs) and Additional Hours Ventilated (VentHrsA) are also new to the 2.41 data specifications.  These fields can not contain a value of zero because each one has a parent field (Readmission to ICU and Re-Intubated During Hospital Stay, respectively) that determines whether or not a value should be collected.  If the parent value is Yes, then the field value will start with at least one.