Return

Коагулограмма №1 (протромбин (по Квику), МНО)

Code:3004

Synonyms
Протромбинпротромбиновый индексмеждународное нормализованное отношениеINRInternational normalized ratioPTProthrombinProthrombin indexProtime

Analysis details

Methodology

—

Expected Turnaround Time

1 day

Special Instructions

  • For infants younger than 1 year, avoid feeding for 30–40 minutes before collection.
  • For children 1–5 years old, do not give food for 2–3 hours before the test.
  • For older children and adults, fast for 12 hours; plain, noncarbonated water is permitted.
  • Avoid vigorous physical activity and emotional stress for 30 minutes prior to sampling.
  • Do not smoke during the 30 minutes before specimen collection.

How to use

The PT/INR (Prothrombin, Quick percent, and International Normalized Ratio) test is used to manage therapy with indirect anticoagulants (vitamin K antagonists), helping to balance anticoagulation with bleeding risk. It also assists in assessing activity within the extrinsic pathway, including factor VII, by reporting Quick prothrombin percentage and the standardized INR value.

Limitations

Prothrombin testing evaluates the extrinsic arm of the coagulation cascade. Results are typically reported as Quick prothrombin percentage and as the International Normalized Ratio (INR). Quick percentage is derived from a calibration curve constructed using serial dilutions of normal plasma; because this approach is not standardized across reagents and instruments, it is primarily used to appraise factors in the extrinsic activation pathway. The INR provides a standardized metric by expressing the patient’s prothrombin ratio—patient prothrombin time divided by the mean normal prothrombin time—raised to the International Sensitivity Index (ISI) of the thromboplastin in use. INR enables consistent interpretation of anticoagulation intensity regardless of thromboplastin reagent and facilitates comparison of results between laboratories. It is used to gauge the degree of hypocoagulation during treatment with indirect anticoagulants (eg, warfarin). Target INR ranges are defined by clinical indication according to international guidance.

Reference interval
ParameterMinMax
МНО (INR - International Normalized Ratio)0.81.2
ISI Value (Международный индекс чувствительности реагента)–1
IndicationsMonitoring patients receiving vitamin K antagonists (indirect anticoagulants), such as warfarin, Screening assessment of coagulation with emphasis on the extrinsic pathway

Possible Causes of Abnormal Results

Increased levels

  • fibrin degradation products
  • paraproteins

Specimen Requirements

SpecimenPlasma
ContainerLight Blue Top (3.2% Sodium Citrate)

References

Lifshits VM, Sidelnikova VI. Biochemical Tests in the Clinic: A Handbook. 2nd ed. Moscow: Medical Information Agency; 2001:303.

Dolgov VV, Svirin PV. Laboratory Diagnosis of Hemostasis Disorders. Moscow–Tver: Triada; 2005:227.

Nazarenko GI, Kishkun AA. Clinical Evaluation of Laboratory Test Results. Moscow: Meditsina; 2006:543.