Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 4 complete abstracts (810 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
System established by the World Health Organization and the International Committee on Thrombosis and Hemostasis for monitoring and reporting blood coagulation tests. Under this system, results are standardized using the International Sensitivity Index for the particular test reagent/instrument combination used.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: International Normalized Ratios; Normalized Ratio, International; Normalized Ratios, International; Ratio, International Normalized; Ratios, International Normalized; INR.
Where it fits in the MeSH classification
- Broader topics
- Blood Coagulation Tests
- See also
- Blood Coagulation
Research landscape
PubMed indexes 6,472 records tagged with the MeSH heading “International Normalized Ratio” (counts retrieved 2026-11-04). 953 of them (14.7%) were published from 2020 onward, and the busiest period so far is 2010-2019 with 3,225 records.
Reviews account for 681 records (10.5%) and meta-analyses for 98. Randomized controlled trials number 482 (7.4%) as a share of all records on the topic.
Show the data
| Period | Records |
|---|---|
| through 1999 | 138 |
| 2000-2009 | 2,156 |
| 2010-2019 | 3,225 |
| 2020 onward | 953 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 681 | 10.5% |
| Meta-analyses | 98 | 1.5% |
| Randomized controlled trials | 482 | 7.4% |
Method: PubMed query "International Normalized Ratio"[MeSH Terms] with publication-type and date filters, retrieved 2026-11-04.
Reading the evidence in diagnostics and medical technology
A test or device is judged by how well it detects a condition, how often it gives false alarms or misses cases, and whether using it improves outcomes for people. Accuracy depends on who is tested and how common the condition is, so a test that performs well in a specialist hospital can perform differently in the community. Check the reference standard, the population studied, the sensitivity and specificity and whether results were confirmed in a separate group.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| Fixed Versus Variable Dosing of Prothrombin Complex Concentrate in Vitamin K Antagonist-Related Intracranial Hemorrhage: A Retrospective Analysis | 2017 | Research article Design not recorded in structured metadata | 34 | cc by PMID 27052728 · DOI · PMC5226998 |
| Center-Related Determinants of VKA Anticoagulation Quality: A Prospective, Multicenter Evaluation | 2015 | Research article Design not recorded in structured metadata | 17 | cc by PMID 26636337 · DOI · PMC4670074 |
| Micro-mechanical blood clot testing using smartphones | 2022 | Research article Design not recorded in structured metadata | 16 | cc by PMID 35149711 · DOI · PMC8837659 |
| In vitro Study of the Effects of Acetylcysteine on the International Normalized Ratio Over Time | 2026 | Research article Design not recorded in structured metadata | 0 | cc by PMID 40663728 · DOI · PMC13152081 |
Fixed Versus Variable Dosing of Prothrombin Complex Concentrate in Vitamin K Antagonist-Related Intracranial Hemorrhage: A Retrospective Analysis [1]
Abstract reading summary — source excerpts
- Opening excerpt
- BackgroundMillions of patients receive vitamin K antagonist (VKA) therapy worldwide.
- Closing excerpt
- The effect on clinical outcome remains unknown.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (259 words)
BackgroundMillions of patients receive vitamin K antagonist (VKA) therapy worldwide. Annually 0.2-1 % of all VKA users develops an intracranial hemorrhage (ICH). Prothrombin complex concentrate (PCC) is administered to restore the INR ≤ 1.5 in an attempt to limit hematoma growth. In order to facilitate PCC dosing, our hospital recently changed from a variable dose based on bodyweight, baseline- and target-INR, to a fixed 1000 IU fIX PCC dosing protocol for ICH.MethodsIn a before and after design, we compared successful achievement of an INR ≤ 1.5 with a fixed dosing strategy versus the variable dosing strategy of PCC in patients presenting with intracranial bleeding complications of VKA. Data of the two cohorts of patients were retrospectively collected from medical records.ResultsA median dosage of 1750 IU was given per patient in the variable dose group (n = 25) versus 1000 IU in the fixed dose group (n = 28). In the intention-to-treat analysis, 96 % achieved an INR ≤ 1.5 after an initial dose in the variable dose cohort compared to 68 % in the fixed dose cohort (p = 0.01). An additional dose was given in 2 (8 %) versus 9 (32 %) patients, respectively (p = 0.04). The median door-to-PCC-order time was 42 versus 32 min (p = 0.37) and the door-to-needle time was 81, respectively 60 min (p = 0.42).ConclusionThe fixed dose protocol necessitates additional PCC infusions more frequently to achieve a target INR ≤ 1.5. Door-to-order and door-to-needle time were shorter but, in this small cohort, not significantly so. The effect on clinical outcome remains unknown.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 27052728 · DOI · PMC5226998
Center-Related Determinants of VKA Anticoagulation Quality: A Prospective, Multicenter Evaluation [2]
Abstract reading summary — source excerpts
- Opening excerpt
- BackgroundCenter-specific TTR (c-TTR) is a measure reporting the mean patient TTR within an anticoagulation clinic describing the quality of anticoagulant monitoring offered by that clinic.
- Closing excerpt
- ConclusionsThese findings suggest that c-TTR associates with proactive strategies aimed at keeping patients very close to their target INR with a prompt re-evaluation of those patients with under- or over-therapeutic INR.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (208 words)
BackgroundCenter-specific TTR (c-TTR) is a measure reporting the mean patient TTR within an anticoagulation clinic describing the quality of anticoagulant monitoring offered by that clinic. c-TTR has a considerable between-center variation, but its determinants are poorly understood.ObjectivesWe aimed at evaluating which clinical, procedural or laboratory factors could be associated with c-TTR variability in a multicenter, observational cross-sectional study over a five-year period.Patients/methodsData from 832,204 individual patients followed for VKA therapy in 292 Centers affiliated with the Italian Federation of Anticoagulation Clinics (FCSA) were analyzed. c-TTR was computed based on the TTR of patients followed at each Center, and a mixed linear regression model was used for a predefined set of explanatory variables.ResultsThe Center next-visit interval ratio (the mean number of days after a visit with an INR outside the therapeutic range, divided by the days after a visit with an INR within the therapeutic range), the Center mean patient INR and the Center laboratory performance at EQA proficiency testing were the only variables that were independently associated with c-TTR (β-coefficients -17.32, 9.67, and -0.11, respectively; r2 = 0.635).ConclusionsThese findings suggest that c-TTR associates with proactive strategies aimed at keeping patients very close to their target INR with a prompt re-evaluation of those patients with under- or over-therapeutic INR.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 26636337 · DOI · PMC4670074
Micro-mechanical blood clot testing using smartphones [3]
Abstract reading summary — source excerpts
- Opening excerpt
- Frequent prothrombin time (PT) and international normalized ratio (INR) testing is critical for millions of people on lifelong anticoagulation with warfarin.
- Closing excerpt
- Given the ubiquity of smartphones in the global setting, this proof-of-concept technology may provide affordable and effective PT and INR testing in low-resource environments.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (150 words)
Frequent prothrombin time (PT) and international normalized ratio (INR) testing is critical for millions of people on lifelong anticoagulation with warfarin. Currently, testing is performed in hospital laboratories or with expensive point-of-care devices limiting the ability to test frequently and affordably. We report a proof-of-concept PT/INR testing system that uses the vibration motor and camera on smartphones to track micro-mechanical movements of a copper particle. The smartphone system computed the PT/INR with inter-class correlation coefficients of 0.963 and 0.966, compared to a clinical-grade coagulation analyzer for 140 plasma samples and demonstrated similar results for 80 whole blood samples using a single drop of blood (10 μl). When tested with 79 blood samples with coagulopathic conditions, the smartphone system demonstrated a correlation of 0.974 for both PT/INR. Given the ubiquity of smartphones in the global setting, this proof-of-concept technology may provide affordable and effective PT and INR testing in low-resource environments.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 35149711 · DOI · PMC8837659
In vitro Study of the Effects of Acetylcysteine on the International Normalized Ratio Over Time [4]
Abstract reading summary — source excerpts
- Opening excerpt
- BackgroundPatients with paracetamol poisoning are treated with acetylcysteine.
- Closing excerpt
- Additionally, a large interindividual variability was observed.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (193 words)
BackgroundPatients with paracetamol poisoning are treated with acetylcysteine. In paracetamol-poisoned patients without hepatocellular injury, an increased international normalized ratio (INR) was observed after acetylcysteine administration. Because INR is a marker of liver injury in paracetamol poisoning, assessing the magnitude of the effect of acetylcysteine treatment on INR is crucial. This in vitro study aimed to quantify the effects of clinically relevant concentrations of acetylcysteine on INR over time.MethodsAcetylcysteine (0-500 mg/L) in Omniplasma (pooled plasma) or citrate plasma from 6 healthy subjects was incubated at 37°C for up to 24 or 6 hours, respectively. Combined with acetylcysteine, the effects of paracetamol (0-200 mg/L), incubation temperature (37, 20, and 4°C), and tube size (15 and 2.5 mL) were investigated. Samples were drawn frequently and analyzed for INR. Citrate plasma from healthy subjects was used to assess interindividual variability. Data were analyzed using a generalized linear mixed model.ResultsAt 37°C, every mmol/L (equals 163 mg/L) of acetylcysteine increased the INR with 0.039 (99% confidence interval [CI] 0.032-0.046, P ConclusionsThis in vitro study showed a clinically significant effect of increasing acetylcysteine concentrations on INR over time at 37°C in pooled plasma. Additionally, a large interindividual variability was observed.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40663728 · DOI · PMC13152081
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article How to interpret and pursue an abnormal prothrombin time, activated partial thromboplastin time, and bleeding time in adults [5]
- Research article Review article: the prothrombin time test as a measure of bleeding risk and prognosis in liver disease [6]
- Research article Optimal INR for prevention of stroke and death in atrial fibrillation: a critical appraisal [7]
- Research article Standardization of Prothrombin Time/International Normalized Ratio (PT/INR) [8]
- Research article Precision and accuracy of point-of-care testing coagulometers used for self-testing and self-management of oral anticoagulation therapy [9]
- Research article Guidelines on preparation, certification, and use of certified plasmas for ISI calibration and INR determination [10]
References
- Abdoellakhan RA, Miah IP, Khorsand N, Meijer K, Jellema K. Fixed Versus Variable Dosing of Prothrombin Complex Concentrate in Vitamin K Antagonist-Related Intracranial Hemorrhage: A Retrospective Analysis. . 2017. PMID 27052728 · DOI · PMC5226998
- Tosetto A, Manotti C, Marongiu F, Italian Federation of Anticoagulation Clinics (FCSA) clinical quality study group. Center-Related Determinants of VKA Anticoagulation Quality: A Prospective, Multicenter Evaluation. . 2015. PMID 26636337 · DOI · PMC4670074
- Chan J, Michaelsen K, Estergreen JK, Sabath DE, Gollakota S. Micro-mechanical blood clot testing using smartphones. . 2022. PMID 35149711 · DOI · PMC8837659
- Nazar M, Kootstra-Ros JE, Touw DJ, Sturkenboom MGG. In vitro Study of the Effects of Acetylcysteine on the International Normalized Ratio Over Time. . 2026. PMID 40663728 · DOI · PMC13152081
- Kamal AH, Tefferi A, Pruthi RK. How to interpret and pursue an abnormal prothrombin time, activated partial thromboplastin time, and bleeding time in adults. Mayo Clin Proc. 2007. PMID 17605969 · DOI
- Tripodi A, Caldwell SH, Hoffman M, Trotter JF, Sanyal AJ. Review article: the prothrombin time test as a measure of bleeding risk and prognosis in liver disease. Aliment Pharmacol Ther. 2007. PMID 17593061 · DOI
- Odén A, Fahlén M, Hart RG. Optimal INR for prevention of stroke and death in atrial fibrillation: a critical appraisal. Thromb Res. 2006. PMID 16517250 · DOI
- Dorgalaleh A, Favaloro EJ, Bahraini M, Rad F. Standardization of Prothrombin Time/International Normalized Ratio (PT/INR). Int J Lab Hematol. 2021. PMID 32979036 · DOI
- Christensen TD, Larsen TB. Precision and accuracy of point-of-care testing coagulometers used for self-testing and self-management of oral anticoagulation therapy. J Thromb Haemost. 2012. PMID 22118602 · DOI
- van den Besselaar AM, Barrowcliffe TW, Houbouyan-Réveillard LL, Jespersen J, Johnston M, Poller L, et al.. Guidelines on preparation, certification, and use of certified plasmas for ISI calibration and INR determination. J Thromb Haemost. 2004. PMID 15550026 · DOI
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-11-04; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-11-04.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.