Dear Hocine,

The following site may be helpful to be updated on INR cases:

https://labtestsonline.org/understanding/analytes/pt/tab/test/

Hoping this will be helpful,

Rafik

Dear Hocine,

Herein some other references:

1-J Lab Clin Med. 1996 Aug;128(2):214-7.

Reliability of the international normalized ratio for monitoring the induction phase of warfarin: comparison with the prothrombin time ratio.

Johnston M1, Harrison L, Moffat K, Willan A, Hirsh J.

Author information

Abstract

The International Normalized Ratio (INR) was introduced to reduce the variability of prothrombin time (PT) reporting. One potential problem with the use of the INR is the assumption that its reliability is reduced when it is used to monitor patients during the induction phase of treatment. This shortcoming arises because the model used to establish the INR system is based on the use of pooled plasma from patients stabilized on warfarin for at least 6 weeks. Because the prolongation of the PT by warfarin during the induction phase mainly reflects reduction in factor VII levels (whereas the prolongation of the PT after 6 weeks of stabilization reflects reductions in factors X, II, and VII), there exists a potential for loss of accuracy of the INR during warfarin induction. To overcome this potential problem, it has been suggested that the PT ratio should be used to report results during the induction phase of treatment and that the INR system should be reserved for reporting results after the patient has been stabilized. This approach is confusing to the clinician. In addition, the validity of this approach has never been demonstrated in a clinical study. To address this issue, we studied 43 patients for the first 5 days after they started warfarin therapy. We measured the PT in the same plasma samples from each patient with five different commercial thromboplastins. The variance in the PT ratios among the five thromboplastins was compared with the variance obtained with the INR values derived from the PT ratios when using the international sensitivity indexes provided by the manufacturer. Our results indicate that, even during the induction phase, there is less variance with the INR system than with the PT ratio system.

http://www.ncbi.nlm.nih.gov/pubmed/8765218

2-Arch Intern Med. 1994 Feb 14;154(3):282-8.

The international normalized ratio. A guide to understanding and correcting its problems.

Hirsh J1, Poller L.

Author information

Abstract

With the increasing use of the international normalized ratio (INR) to monitor warfarin therapy, a number of problems with prothrombin time (PT) testing have been identified that have led some laboratory physicians to question the reliability of the INR. This is ironic, because it was the introduction of the INR system that brought to light some of the long-standing problems with the technique of PT monitoring. However, these problems are not insurmountable if a compromise can be reached between the expectations of laboratory physicians and of clinicians. Thus, the laboratory physician seeks a perfect assay system, which in the case of the INR is unattainable at present, because of differences in PT reagents and methods. In contrast, the clinician is satisfied with a system of monitoring that provides safe and effective warfarin dosing. This goal can be achieved provided that certain details of PT testing are observed. In this communication, which is directed to practicing clinicians, the potential problems with the INR system are discussed, their clinical relevance is critically reviewed, and solutions are offered.

http://www.ncbi.nlm.nih.gov/pubmed/8297194

3- The International Normalized Ratio: How well do we understand this measurement?

Author: Neil Harris, MD  // Date: SEP.4.2012  // Source: NACB

Topics: Markers

The oral anticoagulant warfarin (also called coumadin) is a vitamin K antagonist that is widely used to prevent venous thrombosis. Warfarin inhibits the post-translational carboxylation of coagulation factors II, VII, IX and X. This diminishes the ability of these factors to interact with phospholipid membranes. The degree of anticoagulation achieved by warfarin is monitored by the common coagulation test known as the prothrombin time (PT). The latter is a clot-based test carried out on citrated plasma. The PT is initiated by adding tissue factor in (supraphysiologic concentrations) along with phospholipids and calcium chloride. The tissue factor/phospholipid combination is called thromboplastin. The PT does not prolong in response to deficiencies all the coagulation factors - for example, it is unaffected by low FVIII & FIX in patients with hemophilia.

https://www.aacc.org/community/national-academy-of-clinical-biochemistry/scientific-shorts/2012/the-international-normalized-ratio-how-well-do-we-understand-this-measurement

4-Optimal Target International Normalized Ratio For Patients With Mechanical Heart Valves Vink et al. (1) compared the occurrence rates of bleeding and thrombo-embolism among patients with mechanical heart valves who had either high-intensity or low-intensity vitamin K antagonist therapy (VKA). Based on their findings of lower combined bleeding and thrombo-embolic occurrence rates in the high- versus low-intensity VKA group, they concluded that “both aortic and mitral valves will benefit from a treatment strategy with a target INR higher than 3.0.” This is a controversial conclusion because most recent publications recommend a valve-specific and lower target international normalized ratio (INR) (2,3).

Therefore, we closely studied Vink’s analyses and have the following comments

https://www.google.ps/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwiw2vqK7q_LAhWBJ5oKHfHCDokQIAg4MAQ&url=https%3A%2F%2Fwebcache.googleusercontent.com%2Fsearch%3Fq%3Dcache%3AZ19dY2rtcDsJ%3Ahttps%3A%2F%2Fcontent.onlinejacc.org%2Fpdfaccess.ashx%253FResourceID%253D2904636%2526PDFSource%253D13%2B%26cd%3D5%26hl%3Den%26ct%3Dclnk%26gl%3Dps&usg=AFQjCNHt6ycLfxeeBJzLtwWyB3GdAr9cuA&sig2=T4rN5Gh54G-iGP_GgZh92Q

5- Pre-publication historyInternational normalized ratio testing with point-of-care coagulometer in healthy term neonates

Shigeo Iijima*, Toru Baba, Daizo Ueno and Akira Ohishi

*Corresponding author: Shigeo Iijima [email protected]

BMC Pediatrics 2014, 14:179  doi:10.1186/1471-2431-14-179

Pre-publication versions of this article and reviewers' reports

http://www.biomedcentral.com/1471-2431/14/179/prepub

6-POINT-OF-CARE INTERNATIONAL NORMALIZED RATIO (INR) MONITORING DEVICES FOR PATIENTS ON LONG-TERM ORAL ANTICOAGULATION THERAPY

http://www.hqontario.ca/Evidence/Publications-and-OHTAC-Recommendations/Ontario-Health-Technology-Assessment-Series/Point-of-Care-International-Normalized-Ratio-INR-Monitoring-Devices-for-Patients-on-Long-term-Oral-Anticoagulation-Therapy

7-

Scopus Publication Detail

The publication detail shows the title, authors (with indicators showing other profiled authors), information on the publishing organization, abstract and a link to the article in Scopus. This abstract is what is used to create the fingerprint of the publication.

Elevated international normalized ratio as a manifestation of post-thrombolytic coagulopathy in acute ischemic stroke

Vivien H. Lee; James J. Conners; Shawna Cutting; Sarah Y. Song; Richard A. Bernstein; Shyam Prabhakaran

(Profiled Authors: Richard A Bernstein; Shyam Prabhakaran)Journal of Stroke and Cerebrovascular Diseases. 2014;23(8):2139-2144.

Scopus

Full text | 

Abstract© 2014 National Stroke Association.Background A serious complication of intravenous tissue plasminogen activator (tPA) in acute ischemic stroke is hemorrhage. Coagulation factors that may potentially increase the risk of bleeding after tPA are not well understood.

Methods We retrospectively reviewed 284 acute ischemic stroke patients who received tPA. Post-tPA coagulopathy was defined as a documented elevation of international normalized ration (INR) > 1.5 within 24 hours after IV tPA without a known cause.

Results We identified 21 (7.4%) patients with an elevated INR post-thrombolysis. The mean age was 68.3 years (standard deviation ± 11.9) and 57% were male. The mean initial National Institutes of Health Stroke Scale (pre-tPA) was 15.8 (range, 4-35). Liver disease or alcohol abuse was noted in 19%. There were 2 tPA protocol violations who received more than 90 mg tPA. The mean post-tPA INR was 2.03 (range, 1.5-4.7) and the elevation in INR was documented within a mean 5.4 hours (range, 1-15) after tPA initiation. Repeat INR levels returned to normal during their hospital stay in 19 patients. Hypofibrinogenemia was noted in 10 of 12 patients who had fibrinogen levels drawn within 48 hours after tPA initiation and in all 7 patients with fibrinogen levels drawn the same time as the elevated INR. Among the 6 patients with bleeding complications, 2 patients had symptomatic intracerebral hemorrhage.

Conclusions We report an under-recognized early transient coagulopathy associated with elevated INR in stroke patients after treatment with tPA.

http://www.scholars.northwestern.edu/pubDetail.asp?id=84908155089&o_id=60&t=pm

Hoping this will be helpful,

Rafik

Dear Hocine,

Have you ever think about it.

http://www.pharmacytimes.com/publications/issue/2007/2007-04/2007-04-6433