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1. Indicate which feature of a test is addressed
in the statements below.
The reference interval for hematocrit of those who live at higher altitudes
is greater than those who live at lower altitude. A patient from Denver,
Colorado who recently moved to New York City was found to have a chronic
blood loss despite a hematocrit within the reference interval found in
New York City.
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Inside the reference interval is not the same as
disease-free
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Outside the reference interval is not the same
as disease
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Changes within the reference interval may indicate
disease
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The reference interval is not the same as desirable
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An individual's own reference group may have a different reference interval from the reference interval that accompanies the test report |
Correct.
The range of normal or reference interval is a necessary
evil. Ideally we would like to know what an individual's level on
a test should be. Sometimes this is possible by use of their previous
level. Often, however, we need to utilize a reference interval.
Ideally the reference interval reflects the interval of values for
similar individuals.
Sometimes the laboratory will help in this process. For instance, the level of hematocrit is often reported separately for men and women and for children of particular ages. This is the situation since it is well known that these characteristics influence the level of hematocrit.
Not all factors that influence the hematocrit or other tests are
reported by laboratories as separate reference intervals. The increase
in hematocrit for those living at high altitude may be reflected
in the reference interval reported in Denver but it is unlikely
to be reported as a separate reference interval in New York City.
Thus, this individual's own reference group may be different from
the reference interval that accompanies the test report.
