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  3. Prolonged coagulation time will be noted in afibrinogenemia and marked hyperheparinemia. Interfering Factors 1. Quality of venipuncture: The venipuncture must be carefully done because either tissue thromboplastin obtained as a contaminant when the venipuncture is done, or hemolyzed red blood cells suctioned when the blood is drawn, can cause a marked shortening of the coagulation time. The time required for a severe hemophiliac’s blood to clot can be shortened from 1 hour to a normal value when a poor venipuncture is done. Clinical Hematology: Bleeding Disorders 277 2. Type of test tube: The coagulation time will be lengthened to 20 to 40 minutes if plastic or silicone coated test tubes are used. 3. Drugs: Increased coagulation time may be seen with: • Mithramycin • Tetracyclines • Anticoagulants • Azathioprine • Carbenicillin.  Decreased coagulation time may be seen with: • Corticosteroids • Epinephrine. Clot Retraction Principle When whole blood is allowed

  ¾ Filter paper ¾ Glass slide ¾ Alcohol sponges. Method 1. Clean the lobe of the ear or tip of a finger with alcohol and let dry. 2. For ear—glass slide is placed behind the ear lobe and held firmly in place. This provides a firm site for incision. 3. Pierce the lobe of the ear by a firm stroke against the glass slide (or pierce the finger-tip). Discard the glass slide if ear lobe has been incised. Start the stop watch when the stab was made. 4. Bleeding of the wound should be allowed to proceed without pressure and the blood is allowed to drop on the filter paper. The paper should be moved so that each drop will fall on a fresh area. When bleeding slows, the wound is touched gently with a fresh area of the filter paper at 30 second intervals. When blood no longer stains the filter paper, the watch is stopped and the time recorded. Normal Values The normal range is up to 6 minutes. Between 6 and 10 minutes, the results are borderline. Over 10 minutes is definitely abnormal. Precaution

  Cumulative Sum (Cusum) Charting was introduced in 1960s. Deviation from the largest is plotted in a cumulative manner so that each point represents the sum of all the deviations to date from the mean or target value. This method of plotting exaggerates trends in data and makes shifts of the mean much more obvious than by other plots. The rules for using the Cusum system for quality control are less well defined than for the L-J system. Duplicate Tests A well-known method for checking precision in clinical analysis is duplicate testing. In this process, a few of the specimens that were measured in an earlier batch, are rechecked with the next batch control. Inbuilt Quality Control This includes: ¾ These of cumulative reports of a single patient ¾ Clinical correlation: If a physician can not interpret a report on clinical grounds, a repeat test with a fresh specimen is indicated ¾ Red cell indices: If reports are giving erroneous rise or fall in the red cells indices, this usually poin