Missing Data
    It is important to keep in mind that there is a difference between a 
        negative value and a missing value.  In most cases, a missing value indicates that an 
        assessment/condition was not provided.  A negative value means that 
        an assessment/test was conducted but the condition was not observed.  A 
        value of [N/A] ('not available' or 'not applicable') is the same as 
        a missing value.
    
        Example
        A screening assessment of Tibial Torsion may have three possible values: Positive, 
            Negative, and [N/A].  If the test was performed but torsion was not 
            observed, then the data recorded is 'negative'.  If the test was not 
            performed or conducted, then the value should be left blank (missing) or [N/A] can be specified.
    
    In the case of screening, assessments 
        that were skipped should be left blank or marked [N/A].  
    Exception
    The only exception to the above missing data issue is with technique screening data.  
        Missing technique data may mean one of two things
    
        - The condition was not observed.
- The test was not conducted.