The Technic of a Blood Examination
The first requisite to the study of a blood dyscrasia is a complete and accurate laboratory examination of the blood. The presence of an anemia, leukemia or other disease of the blood may be suggested by the history and physical examination, yet no clinician would hazard a final diagnosis or outline treatment without knowing the results of the laboratory studies. Too often the clinician expresses an opinion based on blood films which are unsatisfactory for examination or on incomplete or inaccurate laboratory data. The selection of the best technical methods is difficult for those who are not constantly studying problems in hematology, although the technical study of blood is simple and requires no complicated apparatus. The methods described here have proven most dependable in our hands.
A routine blood count (red and white cell count, hemoglobin estimation and differential count) is only a starting point for a more complete blood study and should be looked upon largely as a means of determining whether or not a complete blood study is indicated. In every case of anemia the following examinations should be done:
Red corpuscle count.
Determination of the mass of packed corpuscles.
Calculation of indices:
Volume index (erythrocyte volume relative to normal) or mean corpuscular volume.
Color index (erythrocyte hemoglobin relative to normal) or mean corpuscular hemoglobin content.
Saturation index (concentration of hemoglobin per unit volume of packed cells relative to normal) or mean corpuscular hemoglobin concentration.
White corpuscle count.