Place of biochemical tests in aircrew medical examinations. 
The availability of sophisticated tests to quantify the function of various organs has led to the inclusion of a battery of biochemical tests in the medical examinations for aircrew.  The purpose of these tests is to detect disease before it is clinically apparent so that its natural course may be altered by treatment.  Even if no definitive treatment exists, the presence of a disease may alter an individual's aircrew status.  A laboratory test is only useful if it answers questions that relate to patient management.  The question addressed by each test should be clearly stated and the sensitivity and specificity of the test should be known.  Unfortunately, many of the tests used do not suit the purpose for which they are employed as they lack efficiency.  It is also important to understand how the tests may be set to influence the rate of false-positive and false-negative results.  Most patients with positive tests may not have the target disorder and each will require a definitive evaluation and diagnosis.  If we are unable to arrive at these diagnoses, our efforts in screening will be wasted; only aircrew will remain who have been told they might have something wrong with them, and a flight surgeon who does not know whether they are fit for flying duty or not!