International normalised ratio

Paracetamol is indicated as an anti-pyretic and may be safely administered in a patient on warfarin. A topical nasal decongestant is effective for rhinorrhoea (runny nose) and would not interfere with warfarin. Altering the dose of warfarin is only recommended on the basis of results of international normalised ratio (INR) levels. 

The clotting screen, which includes prothrombin time (PT) and international normalised ratio (INR), is not part of the standard LFT but is essential for the assessment of a patient s liver fimction. As the liver is responsible for synthesising clotting factors this is the key marker for determining and monitoring liver function trends. 

The prothrombin time (FT), which is usually expressed as the International Normalised Ratio (INR) for control of oral anticoagulant therapy, primarily evaluates the extrinsic system. 

Uses. Warfarin is the oral anticoagulant of choice, for it is reliably effective and has the lowest incidence of adverse effects. Monitoring of therapy is by the prothrombin time. Usually the test is carried out with a standardised thromboplastin and the result is expressed as the International Normalised Ratio (INR), which is the ratio of the prothrombin time in the patient to that in a normal (non-anticoagulated) person—taking account of the sensitivity of the... 

Deitcher S. Interpretation of the international normalised ratio in patients with liver disease. Lancet 2002 359 47-8. 

ND Not detected, AST aspartate aminotransferase, ALT alanine aminotransferase, INR international normalised ratio (blood doting indicator). Bilirubin (T) total bilirubin. Bilirubin (C) conjugated bUirubin, AP alkaline phosphatase, BUN blood urea nitrogen. 

The prothrombin time test (PT, Pro-Time, tissue factor induced coagulation time) is the most eommon method employed in clinical situations. It measures the time taken for a fibrin elot to form in a citrated plasma sample eontaining ealeium ions and tissue thromboplastin. The PT is usually reported as the International Normalised Ratio (INR). 

International normalised ratio (INR). The DSTR was adopted by the WHO in 1982 to standardise (using the International Sensitivity Index) oral anticoagulant therapy to take into account the sensitivities of the different thromboplastins used in laboratories across the world. The formula for calculating the INR is as follows ... 

International normalised ratio 0.9 to 1.2 2 to 4 depending on indication for anticoagulation... 

A 60-year-old Caucasian lady presented initially with a 2-day history of pruritus and dark urine after taking black cohosh for menopausal symptoms for 2 weeks. Her blood test results showed bilirubin 474 mmol/L (normal range 3-20), alkaline phosphatase 151 lU/L (normal 30-130), aspartate transaminase 2385 lU/L (normal 10-50) and international normalised ratio 1.57. Atransjugular liver biopsy was performed which showed confluent multiacinar parenchymal collapse with ductular reaction and non-specific inflammation. The patient underwent an orthotopic liver transplantation later and made a successful recovery. 

Whatever the interventional procedure, it is vital that the patient comes to the interventional room in the best possible state to reduce risk and ensure success. Care should be taken to ensure adequate hydration to maintain renal function, and anaemia and clotting abnormalities need to be corrected. As a guide the following values should be regarded as desirable haemoglobin > 100 g/1, platelets > 50.000/ pi, PT-ratio (international normalised ratio, INR) and APTT ratio < 1.3. 

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