IgG4-related cholangitis - a mimicker of fibrosing and malignant cholangiopathies.

IgG4-related cholangitis (IRC) is the major hepatobiliary manifestation of IgG4-related disease (IgG4-RD), a systemic fibroinflammatory disorder. The pathogenesis of IgG4-RD and IRC is currently viewed as multifactorial, as there is evidence of a genetic predisposition while environmental factors, such as blue-collar work, are major risk factors. Various autoantigens have been described in IgG4-RD, including annexin A11 and laminin 511-E8, proteins which may exert a partially protective function in cholangiocytes by enhancing secretion and barrier function, respectively. For the other recently described autoantigens, galectin-3 and prohibitin 1, a distinct role in cholangiocytes appears less apparent. In relation to these autoantigens, oligoclonal expansions of IgG4+ plasmablasts are present in patients with IRC and disappear upon successful treatment. More recently, specific T-cell subtypes including regulatory T cells, follicular T helper 2 cells, peripheral T helper cells and cytotoxic CD8+ and CD4+ SLAMF7+ T cells have been implicated in the pathogenesis of IgG4-RD. The clinical presentation of IRC often mimics other biliary diseases such as primary sclerosing cholangitis or cholangiocarcinoma, which may lead to inappropriate medical and potentially invalidating surgical interventions. As specific biomarkers are lacking, diagnosis is made according to the HISORt criteria comprising histopathology, imaging, serology, other organ manifestations and response to therapy. Treatment of IRC aims to prevent or alleviate organ damage and to improve symptoms and consists of (i) remission induction, (ii) remission maintenance and (iii) long-term management. Glucocorticosteroids are highly effective for remission induction, after which immunomodulators can be introduced for maintenance of remission as glucocorticosteroid-sparing alternatives. Increased insight into the pathogenesis of IRC will lead to improved diagnosis and novel therapeutic strategies in the future.

Annexin A11 is targeted by IgG4 and IgG1 autoantibodies in IgG4-related disease.

OBJECTIVE: Immunoglobulin G4-related disease (IgG4-RD) is a multiorgan immune-mediated disease that predominantly affects the biliary tract (IgG4-associated cholangitis, IAC) and pancreas (autoimmune pancreatitis, AIP). We recently identified highly expanded IgG4+ B-cell receptor clones in blood and affected tissues of patients with IAC/AIP suggestive of specific (auto)antigenic stimuli involved in initiating and/or maintaining the inflammatory response. This study aimed to identify (auto)antigen(s) that are responsible for the clonal expansion of IgG4+ B cells in IgG4-RD. DESIGN: We screened sera of patients with IAC/AIP (n=50), in comparison to control sera of patients with primary sclerosing cholangitis (PSC) and pancreatobiliary malignancies (n=47), for reactivity against human H69 cholangiocyte lysates on immunoblot. Subsequently, target antigens were immunoprecipitated and analysed by mass spectrometry. RESULTS: Prominent reactivity against a 56 kDa protein was detected in human H69 cholangiocyte lysates exposed to sera of nine patients with IAC/AIP. Affinity purification and mass spectrometry analysis identified annexin A11, a calcium-dependent phospholipid-binding protein. Annexin A11-specific IgG4 and IgG1 antibodies were only detected in serum of patients with IgG4-RD of the biliary tract/pancreas/salivary glands and not in disease mimickers with PSC and pancreatobiliary malignancies. Epitope analysis showed that two annexin A11 epitopes targeted by IgG1 and IgG4 autoantibodies were shared between patients with IAC/AIP and IgG4 antibodies blocked binding of IgG1 antibodies to the shared annexin A11 epitopes. CONCLUSION: Our data suggest that IgG1-mediated pro-inflammatory autoreactivity against annexin A11 in patients with IgG4-RD may be attenuated by formation of annexin A11-specific IgG4 antibodies supporting an anti-inflammatory role of IgG4 in IgG4-RD.

On the role of IgG4 in inflammatory conditions: lessons for IgG4-related disease.

The pathophysiology of immunoglobulin G4-related disease (IgG4-RD) and its most common manifestations, IgG4-associated (sclerosing) cholangitis and autoimmune pancreatitis, remains largely unknown, but IgG4 is presumably involved. IgG4 is a promiscuous antibody, which could be directly pathogenic, fulfill a protective role, or could just be a fortuitous marker of an aberrant inflammatory response. IgG4 antibodies possess exclusive structural and functional characteristics suggesting anti-inflammatory and tolerance-inducing effects. By studying the role of IgG4 in other inflammatory conditions, namely hypersensitivity and allergies, autoimmune and immune-mediated diseases, infections and malignancies, new insights can be obtained increasing our understanding of the role of IgG4 antibodies in IgG4-RD. Beekeepers, animal laboratory workers and individuals undergoing allergen immunotherapy possess high serum levels of allergen-specific IgG4, which exhibit immunosuppressive functions, protecting the individual from anaphylactic reactions. In autoimmune/immune-mediated diseases, such as pemphigus vulgaris, pemphigus foliaceus and MuSK-myasthenia gravis, IgG4 autoantibodies are pathogenic. Regarding malignancies such as melanoma and cholangiocarcinoma or helminthic infections, IgG4 antibodies inhibit clearance of tumor cells or the invader, respectively. Translating these findings to IgG4-RD, IgG4 alone can implement pathogenic effects and structural damage, but may also function as a protective antibody dampening the more harmful effects of IgG1 when directed against the same epitopes. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

IgG4-Associated Cholangitis in Patients Resected for Presumed Perihilar Cholangiocarcinoma: a 30-Year Tertiary Care Experience.

BACKGROUND: Distinguishing perihilar cholangiocarcinoma (PHC) from benign forms of sclerosing cholangitis affecting the hilar bile ducts is challenging, since histological confirmation of PHC is difficult to obtain and accurate non-invasive diagnostic tests are not available. IgG4-associated cholangitis (IAC), an imitator of PHC, may present with clinical and radiographical signs of PHC. IAC can be accurately diagnosed with a novel qPCR test. The aim of this study was to investigate the incidence and long-term activity of IAC in patients resected for PHC in a single tertiary center over a period of 30 years. METHODS: All patients with benign disease who underwent surgery for presumed PHC in our institute between 1984 and 2015 were identified. Benign liver and bile duct specimens were re-evaluated by a pathologist and scored according to international consensus pathology criteria for IgG4-related disease (IgG4-RD). Patients with benign disease still alive were followed-up and a clinical diagnosis of IAC was made using a combination of the HISORt group C (response to steroids) criteria and elevated serum IgG4 levels and/or the novel IgG4/IgG RNA ratio. Also, recurrent symptomatic disease at any time after surgery requiring immunosuppression was assessed. RESULTS: Out of 323 patients who underwent surgery for presumed PHC, 50 patients (15%) had benign disease. In 42% (n = 21/50) of these patients a histological (n = 17) or clinical (n = 4) diagnosis of IAC was established. The remaining patients were diagnosed with unclassified sclerosing inflammation, cystadenoma, or sclerosing hemangioma. Nine out of 12 IAC patients who were followed-up showed episodes of recurrent disease requiring immunosuppressive treatment. CONCLUSIONS: Liver and bile duct resections for PHC during three decades disclosed in 15% benign biliary disorders mimicking PHC of which 42% were definitely diagnosed as IAC. IgG4-RD remains active in the majority of patients with IAC years after surgery. Novel diagnostic tests for IAC might reduce misdiagnosis, unnecessary surgery, and life-threatening complications.

Immunoglobulin G4(+) B-cell receptor clones distinguish immunoglobulin G 4-related disease from primary sclerosing cholangitis and biliary/pancreatic malignancies.

UNLABELLED: Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) of the biliary tree and pancreas is difficult to distinguish from sclerosing cholangitis and biliary/pancreatic malignancies (CA). An accurate noninvasive test for diagnosis and monitoring of disease activity is lacking. We demonstrate that dominant IgG4(+) B-cell receptor (BCR) clones determined by next-generation sequencing accurately distinguish patients with IgG4-associated cholangitis/autoimmune pancreatitis (n = 34) from those with primary sclerosing cholangitis (n = 17) and CA (n = 17). A novel, more affordable, and widely applicable quantitative polymerase chain reaction (qPCR) protocol analyzing the IgG4/IgG RNA ratio in blood also achieves excellent diagnostic accuracy (n = 125). Moreover, this qPCR test performed better than serum IgG4 levels in sensitivity (94% vs. 86%) and specificity (99% vs. 73%) and correlates with treatment response (n = 20). CONCLUSIONS: IgG4(+) BCR clones and IgG4/IgG RNA ratio markedly improve delineation, early diagnosis, and monitoring of IgG4-RD of the biliary tree and pancreas. (Hepatology 2016;64:501-507).

IgG4-related disease of the biliary tract and pancreas: clinical and experimental advances.

PURPOSE OF REVIEW: IgG4-related disease (IgG4-RD) is an immune-mediated disease of unknown cause. It predominantly affects the biliary tract [IgG4-associated cholangitis (IAC)] and pancreas [autoimmune pancreatitis (AIP)] of mostly elderly men. Accurate diagnostic tests are lacking. Patients benefit from predniso(lo)ne treatment. However, disease relapse is often seen. This review will address pathophysiological aspects and advances in diagnostic and therapeutic strategies. RECENT FINDINGS: The role of IgG1 and IgG4 in the pathophysiology of IgG4-RD was studied in mice which showed more intense organ damage of pancreas and salivary glands when IgG1 rather than IgG4 of patients with IgG4-RD was injected. Coadministration of IgG1+IgG4 led to dampening of IgG1-mediated injury supporting the view that IgG4 exerts immune-dampening effects. IgG4+ B-cell receptor clones identified by next-generation sequencing and the IgG4/IgG RNA ratio in human blood assessed by quantitative PCR were able to accurately distinguish IAC/AIP from primary sclerosing cholangitis or pancreatobiliary malignancies. Long-term treatment with low-dose prednisolone was safe and reduced the number of flare-ups in patients with AIP. SUMMARY: Early diagnosis by a novel accurate and easy-to-use qPCR test may prevent life-threatening complications, unnecessary interventions and fatal course because of misdiagnosis. Prednisolone treatment remains the standard of care in patients with IgG4-RD.

IgG4-Associated Cholangitis--A Mimic of PSC.

IgG4-associated cholangitis (IAC) is an inflammatory disorder of the biliary tract representing a major manifestation of IgG4-related disease (IgG4-RD) often with elevation of serum IgG4 levels, infiltration of IgG4+ plasma cells in the affected tissue and good response to immunosuppressive treatment. Its first description may go back to 150 years ago. The clinical presentation of IAC is often misleading, mimicking other biliary diseases such as primary sclerosing cholangitis (PSC) or cholangiocarcinoma. The HISORt criteria--histopathological, imaging, and serological features (sIgG4), other organ manifestations of IgG4-RD and response to treatment--are the standard for the diagnosis of IAC. In this overview of a recent lecture, we summarize our original findings on IgG4-RD that (i) dominant IgG4+ B-cell clones identified by advanced next generation sequencing (NGS) are highly specific for IgG4-RD (meanwhile confirmed by others), are a highly accurate diagnostic marker to distinguish IgG4-RD from PSC and biliary/pancreatic malignancies and may be crucial in unravelling the pathophysiology of IgG4-RD; (ii) sIgG4/sIgG1 >0.24 have additional diagnostic value in comparison to sIgG4 in differentiating IAC from PSC; (iii) blood IgG4 mRNA is a highly accurate diagnostic marker comparable to NGS and may become an easily available and affordable diagnostic standard for distinguishing IgG4-RD from PSC and biliary/pancreatic malignancies; and (iv) 'blue collar work' with long-term exposure to solvents, paints, oil products or industrial gases may be a risk factor for development of IgG4-RD. These findings may contribute to the understanding of the pathophysiology and to the early diagnosis and adequate treatment of IgG4-RD.

Cluster randomized controlled trial of a simple warfarin maintenance dosing algorithm versus usual care among primary care practices.

Many patients using warfarin are being managed in primary care and typically achieve a lower time in therapeutic range (TTR) for the international normalized ratio (INR) than patients in specialized care. A simple warfarin maintenance dosing tool could assist primary care physicians with improving TTR. We tested whether a simple warfarin maintenance dosing algorithm can improve TTR compared with usual care among Canadian primary care physicians. Primary care practices managing warfarin therapy without an anticoagulation clinic, computer decision support system or patient self-management tools enrolled 10-30 patients with target INR range 2-3. Practices were randomized to manage warfarin maintenance with the algorithm, or as usual in 2009-2010. Primary outcome was the mean individual patient TTR, and was compared between groups with adjustment for clustering within practices. There were 13 practices randomized to the Algorithm and 15 practices to Control, enrolling 240 and 297 patients respectively, with a mean follow-up of 280 days. Mean (standard deviation; SD) TTR before the study was comparable between groups [68 % (SD 26) for usual care vs. 70 % (SD 27) for the algorithm; p = 0.49]. Dosing decisions during the study in the algorithm group were more often in agreement with the algorithm's recommendations than with usual care (81 vs. 91 %; p < 0.0001). Mean study TTR of the algorithm group was not superior to usual care: [72.1 (SE 1.7) vs. 71.4 % (SE 1.5) respectively; p = 0.73]. The simple warfarin maintenance dosing algorithm did not improve TTR compared with usual care among Canadian primary care practices.

Galectin-3 and prohibitin 1 are autoantigens in IgG4-related cholangitis without clear-cut protective effects against toxic bile acids.

Background and aims: IgG4-related cholangitis (IRC) is the hepatobiliary manifestation of IgG4-related disease, a systemic B cell-driven fibro-inflammatory disorder. Four autoantigens have recently been described in IgG4-RD: annexin A11, galectin-3, laminin 511-E8, and prohibitin 1. We have previously reported a protective role of annexin A11 and laminin 511-E8 in human cholangiocytes against toxic bile acids. Here, we explored the potentially protective role of the carbohydrate-binding lectin galectin-3 and the scaffold proteins prohibitins 1 and 2. Methods: Anti-galectin-3, anti-prohibitin 1 and 2 autoantibody positivity in IRC and healthy and disease (primary sclerosing cholangitis (PSC)) control sera was assessed by ELISA/liquid chromatography-tandem mass spectrometry (LC-MS/MS). Human H69 cholangiocytes were subjected to short hairpin RNA (shRNA) knockdown targeting galectin-3 (LGALS3), prohibitin 1 (PHB1), and prohibitin 2 (PHB2). H69 cholangiocytes were also exposed to recombinant galectin-3, the inhibitor GB1107, recombinant prohibitin 1, and the pan-prohibitin inhibitor rocaglamide. Protection against bile acid toxicity was assessed by intracellular pH (pHi) measurements using BCECF-AM, 22,23-3H-glycochenodeoxycholic acid (3H-GCDC) influx, and GCDC-induced apoptosis using Caspase-3/7 assays. Results: Anti-galectin-3 autoantibodies were detected in 13.5% of individuals with IRC but not in PSC. Knockdown of LGALS3 and galectin-3 inhibition with GB1107 did not affect pHi, whereas recombinant galectin-3 incubation lowered pHi. LGALS3 knockdown increased GCDC-influx but not GCDC-induced apoptosis. GB1107 reduced GCDC-influx and GCDC-induced apoptosis. Recombinant galectin-3 tended to decrease GCDC-influx and GCDC-induced apoptosis. Anti-prohibitin 1 autoantibodies were detected in 61.5% and 35.7% of individuals with IRC and PSC, respectively. Knockdown of PHB1, combined PHB1/2 KD, treatment with rocaglamide, and recombinant prohibitin 1 all lowered pHi. Knockdown of PHB1, PHB2, or combined PHB1/2 did not alter GCDC-influx, yet knockdown of PHB1 increased GCDC-induced apoptosis. Conversely, rocaglamide reduced GCDC-influx but did not attenuate GCDC-induced apoptosis. Recombinant prohibitin 1 did not affect GCDC-influx or GCDC-induced apoptosis. Finally, anti-galectin-3 and anti-prohibitin 1 autoantibody pretreatment did not lead to increased GCDC-influx. Conclusions: A subset of individuals with IRC have autoantibodies against galectin-3 and prohibitin 1. Gene-specific knockdown, pharmacological inhibition, and recombinant protein substitution did not clearly disclose a protective role of these autoantigens in human cholangiocytes against toxic bile acids. The involvement of these autoantibodies in processes surpassing epithelial secretion remains to be elucidated.

Blue-collar work is a risk factor for developing IgG4-related disease of the biliary tract and pancreas.

BACKGROUND & AIMS: Immunoglobulin G4-related disease (IgG4-RD) of the biliary tract and pancreas is a fibroinflammatory disease of unknown origin with striking male predominance. We aimed to investigate whether blue-collar work and occupational contaminant exposure are risk factors for IgG4-RD of the biliary tract and pancreas. METHOD: We performed an age-/sex-matched case-control study in the largest academic medical centers of the Netherlands. Occupational history was surveyed by questionnaires. The International Standard Classification of Occupations (ISCO88) was used to classify jobs. Job exposure matrices ALOHA and DOM were utilized to assess the years individuals were exposed to compounds. The disease control cohort consisted of patients from 6 equally sized groups. Conditional logistic regression was used to assess effects of blue-collar work and exposure to occupational contaminants on developing IgG4-RD of the biliary tract and pancreas. RESULTS: Overall, 101 patients with IgG4-RD of the biliary tract and pancreas were matched 1:3 to 303 controls. Patients with IgG4-RD had a lower level of education (p = 0.001). Individuals who at least once performed blue-collar work (>1 year), had higher odds of developing IgG4-RD than individuals that only performed white-collar work (odds ratio [OR] 3.66; CI 2.18-6.13; p <0.0001). Being ever exposed (>1 year) to industrial ALOHA (e.g. mineral dust; vapors-dust-gases-fumes) and DOM compounds (e.g. asbestos) resulted in higher odds of IgG4-RD (OR 2.14; 95% CI 1.26-3.16; p <0.001 and OR 2.95; 95% CI 1.78-4.90; p <0.001, respectively). CONCLUSION: Blue-collar work is a risk factor for developing IgG4-RD of the biliary tract and pancreas putatively driven by exposure to selected industrial compounds; this may explain the striking male predominance among patients. LAY SUMMARY: Immunoglobulin G4-related disease (IgG4-RD) causes tumor-like lesions and typically affects middle-aged to elderly men. The background and cause of this disease remain relatively unknown. In this study, we identified blue-collar work as a risk factor for developing IgG4-RD of the biliary tract and pancreas, which may explain the striking male predominance among patients. Furthermore, these results suggest that toxic exposure to occupational contaminants may drive autoimmunity in IgG4-RD of the biliary tract and pancreas.

[The different forms of IgG4-related disease]. / De verschillende vormen van IgG4-gerelateerde ziekte.

Immunoglobulin G4-related disease (IgG4-RD) is a newly recognised immune-mediated disease of unknown origin. IgG4-related disease predominantly affects the pancreas (autoimmune pancreatitis type 1), biliary tract (IgG4-associated cholangitis) and salivary glands. However, based on distinct histopathological findings, IgG4-RD has also been described in nearly every organ of the human body. Patient characteristics include elevated IgG4 serum levels, massive infiltration of lymphocytes - in particular IgG4-positive B and plasma cells - in affected tissues and a good response to immunosuppressive treatment. If left untreated, the chronic inflammation associated with IgG4-RD may lead to fibrosis and organ failure. Here, we discuss diagnostic challenges in two patients who were ultimately diagnosed with IgG4-RD. Additionally, we make suggestions on when to consider a possible diagnosis of IgG4-RD and how to approach the patient, thus enabling early diagnosis and treatment.

How to Diagnose Immunoglobulin G4-Associated Cholangitis: The Jack-of-All-Trades in the Biliary Tract.

BACKGROUND: Immunoglobulin (Ig) G4-associated cholangitis (IAC) is an inflammatory disorder of the biliary tract displaying characteristic features of IgG4-related disease (IgG4-RD): elevation of IgG4 serum levels, infiltration of IgG4+ plasma cells in the affected tissue, and good response to immunosuppressive treatment. METHODS AND RESULTS: The clinical presentation of IAC is often misleading, mimicking other diseases of the biliary tract such as cholangiocarcinoma or primary and secondary sclerosing cholangitis. The HISORt criteria form the cornerstone in the diagnosis of IAC, combining histopathological (H), imaging (I), and serological (S) features including serum IgG4, other organ manifestations (O) of IgG4-RD and response to treatment (Rt). The accuracy of the HISORt criteria is limited. Novel diagnostic approaches are under evaluation. CONCLUSION: More accurate biomarkers are needed to correctly diagnose IgG4-RD and prevent misdiagnoses and unnecessary therapeutic interventions.

IgG4-associated cholangitis: a comprehensive review.

IgG4-associated cholangitis (IAC) is a major manifestation of immunoglobulin G4-related disease (IgG4-RD), an inflammatory multiorgan disorder of unknown cause. IAC and autoimmune pancreatitis (AIP) may mimic sclerosing cholangitis, cholangiocarcinoma, or pancreatic carcinoma. Typically, elderly male patients present with abdominal discomfort, weight loss, jaundice, and itch. At present, no accurate diagnostic test for IAC and IgG4-RD is at hand, often causing significant diagnostic delay. Serum IgG4 is only diagnostic when markedly raised (>4× ULN). Imaging in IAC discloses mass-forming lesions and/or strictures in the biliary tract. Histology may show tissue infiltration of IgG4-expressing plasma cells. Diagnostic criteria for histologic and imaging findings, serum tests, organ manifestation pattern, and response to immunosuppressive therapy (HISORt) criteria are used for the diagnosis of IgG4-RD. Still, considering the difficulty in diagnosing IAC and AIP, unnecessary hepatic or pancreatic resections for presumed malignancies occur. The good response to corticosteroid therapy in IAC and other manifestations of IgG4-RD suggests an immune-mediated inflammatory disease. Maintenance immunosuppression after induction of remission is needed in the majority of patients to avoid relapse. The pathogenesis of IAC and IgG4-RD remains poorly understood. Unresolved questions include: (i) Does IgG4 have a pro- or anti-inflammatory role in IAC? (ii) Is IAC a B cell- and/or T cell-mediated disease? (iii) Which are the molecular targets attacked by the immune system in IgG4-RD? Here, we review the diagnostic and therapeutic management of the disease and discuss recent pathophysiological findings, which might help to better understand the molecular mechanisms contributing to IAC and other manifestations of IgG4-RD.

Quality of individual INR control and the risk of stroke and bleeding events in atrial fibrillation patients: a nested case control analysis of the ACTIVE W study.

INTRODUCTION: Time in therapeutic range (TTR) for international normalized ratio (INR) is an accepted quality measure of anticoagulation control in patient populations, but its usefulness for predicting stroke and bleeding in individuals is not well understood. MATERIALS AND METHODS: In a nested case control analysis among ACTIVE W study patients, cases with stroke and cases with bleeding were separately matched with controls. Several anticoagulation quality measures were compared, overall and in a time-dependent manner. RESULTS: 32 cases with ischemic stroke and 234 cases with bleeding in the analysis were matched in a 4:1 ratio to 122 and 865 controls, respectively. Follow-up duration was 257±154days for the stroke analysis and 222±146days for the bleeding analysis. Compared with their respective controls, the study mean TTR of both stroke cases (53.9%±25.1 vs 63.4%±24.8; p=0.055) and bleeding cases (56.2%±25.4 vs 63.4%±26.8; p<0.001) was lower. Time below range for stroke and time above range for bleeding were only greater in the last month leading up to the event, not over the entire study period. Rather, over the entire study period bleeding cases spent more time below range than controls (26.8%±25.9 vs 20.8%±24.0; p=0.001). CONCLUSIONS: TTR was lower in individual AF patients with stroke or bleeding compared with matched controls in ACTIVE W. Maintaining a high TTR, with equal importance to avoid low and high INRs, is a relevant goal of individual patient treatment to prevent stroke and bleeding.

Randomised comparison of a simple warfarin dosing algorithm versus a computerised anticoagulation management system for control of warfarin maintenance therapy.

Excellent control of the international normalised ratio (INR) is associated with improved clinical outcomes in patients receiving warfarin, and can be achieved by anticoagulation clinics but is difficult in general practice. Anticoagulation clinics have often used validated commercial computer systems to manage the INR, but these are not usually available to general practitioners. It was the objective of this study to perform a randomised trial of a simple one-step warfarin dosing algorithm against a widely used computerised dosing system. During the period of introduction of a commercial computerised warfarin dosing system (DAWN AC) to an anticoagulation clinic, patients were randomised to have warfarin dose adjustment done according to recommendations of the existing warfarin dosing algorithm or to those of the computerised system. The study tested if the computerised system was non-inferior to the existing algorithm for the primary outcome of time in therapeutic INR range of 2.0-3.0 (TTR), with a one-sided non-inferiority margin of 4.5%. There were 541 patients randomised to commercial computerised system and 527 to the algorithm. Median follow-up was 159 days. A dose recommendation was provided and followed in 91% of occasions for the computerised system and in 90% for the algorithm (p=0.03). The mean TTR was 71.0% (standard deviation [SD] 23.2) for the computerised system and 71.9% (SD 22.9) for the algorithm (difference 0.9% [95% confidence interval: -1.4% to 4.1%]; p-value for non-inferiority=0.002; p-value for superiority=0.34). In conclusion, similar maintenance control of the INR was achieved with a simple one-step dosing algorithm and a commercial computerised management system.