Use this screening calculation or category only with a coagulation result measured by the stated method and compared with the matching laboratory control or reference interval.

Patient APTT

A finite measured or assumed value, expressed in s.

Control APTT

A finite measured or assumed value, expressed in s.

The implementation follows this calculation rule: Compute the activated partial thromboplastin time ratio as the patient APTT divided by the control APTT.

APTT ratio

The calculated aptt ratio.

Bleeding and clotting tests do not measure the entire hemostatic system. Reagent sensitivity, specimen collection, anticoagulant therapy, platelet function, reference ranges, and clinical context can change interpretation; this tool is not a diagnosis or treatment recommendation. Ratios and percentages become unstable when their denominator is small, uncertain, or defined differently between samples.

Review the original coagulation panel and local reference range. Depending on the question, platelet count, prothrombin time, fibrinogen, thrombin time, mixing studies, or factor assays may provide the necessary complementary evidence.

• INR Ratio

  Compute the international normalized ratio as (patient PT / mean normal PT)^ISI. Use the International Sensitivity Index assigned to the specific thromboplastin reagent and instrument; the default of one is only appropriate when that is the calibrated ISI.

• Bleeding Time Category

  Classify a bleeding time in minutes up to 30 as normal (<= 7), borderline (<= 15), or prolonged.

• Clotting Time Category

  Flag whether a clotting time between 30 and 600 seconds falls inside the normal range of 90 to 180 seconds inclusive.