Interpretation of laboratory tests in general practice

Blood cell count is one of the most frequently prescribed laboratory tests in general practice. Automatic counters currently in use calculate a number of parameters concerning not only differential leukocyte count, but also some properties of red cells and platelets. They may be very helpful in properly scheduling further diagnostic steps. In some situations (abnormalities of the number or differential leukocyte count, impossibility to determine it automatically, or suspicion of haematological malignancy) the differential leukocyte count should be examined under a microscope. When an abnormality of blood cell count is detected it must be determined whether it arouses the suspicion of haematological disorder, accompanies a non-haematological disease, or has no pathological significance at all. Erythrocyte sedimentation rate (ESR) is another frequently prescribed laboratory test. Its elevation may be due either to numerical or qualitative abnormalities of erythrocytes, or to an increase of serum level of some substance(s), in particular, inflammatory markers or immunoglobulins. If the elevated ESR is found in asymptomatic patients, electrophoresis of serum proteins must be performed to exclude or confirm the presence of monoclonal immunoglobulins, the detection of which justifies the referral of the patient to a haematologist.