For some complex tests there are two ways to organize the results into a report.
3.1.1 Value
Assume a set “X” is made up of five “results” that can have a scale of (absent, present) or (0, 1). These results could be reported as:
| Finding 1 = | Present | or | 1 |
| Finding 2 = | Absent | or | 0 |
| Finding 3 = | Present | or | 1 |
| Finding 4 = | Absent | or | 0 |
| Finding 5 = | Absent | or | 0 |
Each finding is then considered a binary variable. This is sometimes called a “panel” approach.
3.1.2 Variable (multiple choice) approach
The alternative would be to report this information as a single variable (or multiple-choice question) with many possible values:
Variable X – Finding 1, Finding 3
In this case the findings are the values of a variable called Variable X; only the positive findings are reported as values. Many laboratory tests, e.g., those that test for HLA antigens, red blood cell antigens, or screens for toxic substances, could in theory be presented either way. The microscopic part of the differential count and urinalysis could also be described either way. History and physical findings and (given a real stretch) even culture results could be structured in the panel or multiple choice/multiple answer format.
A single lab may report red blood cell antigens in either way, as a binary panel or a multiple-choice result, depending upon the purpose of the test. The routine cross and type are reported out in the multiple choice pattern format (only positives from a modest fixed set of tested antigens are reported). But if the tests are being used to prove fatherhood, the results are usually reported as a binary panel.
Blood cultures could in theory be regarded as panels:
| Test Name | Value |
|---|---|
| Escherichia coli | absent |
| Staphylococcus aureus | present |
| Diphtheroids | absent |
| Streptococcus pneumoniae | absent |
| Pseudomonas aeruginosa | present |
Although in practice such tests are almost always reported in the multiple choice/multiple answer format, as follows:
| Test Name | Values |
|---|---|
| Blood culture | P. aeruginosa, S. aureus |
We bring up these issues to explain why we use a somewhat different data format for some types of tests, and why we sometimes provide for both reporting methods (e.g., HLA blood cell antigen tests) in the LOINC database. When a binary scale is used, the Scale will be ordinal (Ord) and the kind of Property will usually be presence (PrThr, for results based on the presence/absence of an analyte regardless of whether an internal cut off value is used to determine the ordinal result). When the multiple-choice multiple-answer approach is used, the Scale will be nominal (Nom) and the type of Property will be presence or identification (Prid).