In the medical domain, a test is any entity that can be observed by a human or measured by a machine. Clinical laboratory tests are in the latter group. Symptoms and signs are in the former group. A clinical laboratory is a place where the analytical tests are performed although simple lab tests can be done in the doctor's office or at the patient's bedside. For regulatory and quality control reasons, office and bedside tests are not performed as much as they used to be. However, there is a new trend called "point-of-care testing" where miniaturized instruments can be used reliably wherever the patient is located. This trend is expected to grow.

Many laboratory tests can be done by multiple methods, each having different accuracy and precision. To manage these differences, the concept of reference limits is used. Sometimes these are called references ranges, normal ranges, normal limits, etc. In general, this is a probabilistic classification of 95% of a healthy reference population.

The names of clinical laboratory tests are often made up of multiple words and symbols. When looking up a lab test, some of the leading terms may be easier to remember or look up. In this index, the names are permuted, or rotated, circularly so that each important word can be the leading term in the lookup. These permuted terms are then presented alphabetically to facilitate a manual search.

Sometimes the names have special characters. If it makes sense, these will be permuted as well. However, the ones that do not make sense when listed first may be missed. These need to be fixed manually and should be removed in the next version.

Laboratory tests can be performed on all fluids and many solid tissues. Many times the analytical method is the same but the source is different. A serum glucose level has a different meaning than a urine glucose level. The most common sources are whole blood, plasma, serum, and urine. Even though serum and plasma are components of blood, the same analytic method used on these may have a different meaning biologically or chemically.

For clinical laboratory test interpretation, both the test result and its source must be used to derive the proper diagnostic meaning.

The Argo diagnostic software was developed to use laboratory test results to find the shortest list of clinical diagnoses (differential diagnosis). Since the normal values depend on the analytical method, the sample source, the characteristics of the lab, and the characteristics of the population of patients used to derive those values, the results are entered into Argo using ordinal values such as high/low/normal or present/absent or some other appropriate representation. This approach makes test results comparable across laboratories and test methods. The correct treatment depends on making the correct diagnosis.