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Normal results vary based on the method and activators used. Normal APTT results are usually between 25-40 seconds; PTT results are between 60-70 seconds.APTT results for a patient on heparin should be 1.5-2.5 times normal values.An APTT longer than 100 seconds indicates spontaneous bleeding.artial thromboplastin time (PTT), a test for detecting coagulation defects of the intrinsic system by adding activated partial thromboplastin to a sample of test plasma and to a control sample of normal plasma. The time required for the formation of a clot in test plasma is compared with that in the normal plasma.
Reference Range. Partial thromboplastin time (PTT) and activated partial thromboplastin time (aPTT) are used to test for the same functions; however, in aPTT, an activator is added that speeds up the clotting time and results in a narrower reference range.any drugs can change the results of the activated partial thromboplastin time (aPTT), including nonprescription drugs. No specific preparation is required. However, since lipemia may interfere with photoelectric measurements of clot formation, specimens should not be obtained after a meal.