Data Quality: Lab Specimen Source in DSS Laboratory Data

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The Decision Support System (DSS) Laboratory (LAB) and Laboratory Results (LAR) National Data Extracts (NDE) contain information on lab tests performed in the VA and by outside vendors. There is no variable indicating specimen type in either of these datasets. This is a problem when the analyte being tested can be obtained and tested from more than one anatomic source.

Although DSS assigns different intermediate product numbers to tests of the same analyte from different sources, we have found at least one case where the NDE contains tests from different specimen sources under one identifier. This is the creatinine test, whose identification number (the DSSLARNO variable) in the LAR extract is 31. While this test is called “Serum Creatinine” in the DSS Technical Guide (and reproduced in the VIReC DSS Research User Guide), values of the RESULT variable in some records suggest that some of these tests are urine, rather than serum creatinines.

DSS central office personnel are aware of these problems and are working to find a solution. Regardless of potential corrections that may affect future DSS NDEs, the accurate identification of lab test results will continue to be a challenge for researchers working with DSS LAR data from past fiscal years.

A list of lab tests currently available in the DSS LAB and LAR NDEs for which more than one specimen source exists is provided below. We recommend that researchers carefully review the distribution of the values in the RESULT variable to assess their validity. For tests where valid values for different specimen sources do not overlap, it may be possible to deduce the source of the specimen from the test result. Procedures for handling ambiguous cases would need to be developed and employed. In some cases, additional clues regarding specimen source may also be found in the TESTUNIT variable, which contains the unit in which a test result is reported.

The following lab tests, included in the DSS LAB/LAR NDEs, may have more than one specimen source.

* peritoneal, synovial, pleural