Each laboratory has its own characteristic features and hence the quality control approach varies. There are, however, some common features like specimen collection identification and supplies. The manufacturer also plays an important part in providing reliable data by supplying reliable instruments and reagents.
There should be close cooperation between the manufacturer and the laboratory so that the former can meet the needs of the laboratory – of course, for his own profit, but with benefits to the laboratory as well.
Specimens must be processed correctly and test must run within the specified time. Some of the tests must be done within 2 hours (ESR), other within 4 hours (WBC count) and still others can be delayed for 8 to 10 hours (RBC count, PCV or HCt). Fixed smears can be examined after several days.
The maintenance of the equipment must include the checking of centrifuge speed, volume dispensed by the diluters, temperature of the water bath, etc. keep a record of the maintenance plan. Manual RBC count is highly erroneous. Automated counters have their own settings; run the control every day and set the controls according to the manufacturer’s directions.
Correlation of Results:
Is a good way to check on the results? For example, a normal hematocrit should have normal hemoglobin; a strained smear must be correlated with the count and the same holds for a low hemoglobin value; presence of macrocytes and megaloblasts should correspond with increased MCV. It has been found that the indices stay close to the normal values, hence, for standardization use the indices.
The reagent is the biggest source of error in coagulation. Temperature of the water-bath must be checked regularly. All tests run must be accompanied by a control run with normal plasma. Due to lack of appropriate facilities, lyophilized normal plasma is not yet very commonly used in the laboratories of developing countries.
Platelet count per cu mm = Average count of 10 fields under oil-immersion objective X 20000.