Characteristics of alpha-1 antitrypsin deficiency related lung disease exacerbations using a daily symptom diary and urinary biomarkers

BACKGROUND

Pulmonary exacerbations in alpha-1 antitrypsin deficiency (AATD) related lung disease are a significant contributor to disease burden, as with usual COPD. Separating the early stages of an exacerbation from the day-to-day variation in stable COPD is central to the concerns of both clinicians and patients and has been identified as a research priority by NIHR. Clinical tools that distinguish baseline symptoms from those of an exacerbation could allow early and appropriate treatment of AECOPD to reduce the impact and potentially may slow disease progression thereby improving survival and quality of life. Candidate tools include symptom diaries and biomarkers of infection and acute inflammation. Urinary biomarkers of AECOPD have yet to be explored in AATD related COPD.

METHODS

55 patients with AATD related lung disease with a history of 2 or more AECOPD in the preceding year were prospectively followed for 18 months. Each patient recorded symptom scores daily via an electronic symptom diary (eDiary) based on Bronkotest. Urinary biomarkers for AAT, NE, CRP, TIMP1 and desmosine were measured weekly using a home urinary lateral flow device. During self-reported AECOPD patients were asked to perform urine analysis on the first 7 consecutive days.

RESULTS

Type I Anthonisen exacerbations and episodes occurring in autumn/winter lasted longer than Type II/III exacerbations and spring/summer episodes respectively. Median urinary CRP concentration across all study participants increased during Type I AECOPD. eDiary adherence was 68% over a median of 17.8 months (IQR 15.7 to 18.5).

CONCLUSIONS

Use of an eDiary and urinary biomarkers to detect and characterise AECOPD remotely in AATD related lung disease is feasible over a prolonged period and paves the way for precision detection of exacerbations.

Air pollution and COPD: GOLD 2023 committee report

Exposure to air pollution is a major contributor to the pathogenesis of COPD worldwide. Indeed, most recent estimates suggest that 50% of the total attributable risk of COPD may be related to air pollution. In response, the Global Initiative for Chronic Obstructive Lung Disease (GOLD) Scientific Committee performed a comprehensive review on this topic, qualitatively synthesised the evidence to date and proffered recommendations to mitigate the risk. The review found that both gaseous and particulate components of air pollution are likely contributors to COPD. There are no absolutely safe levels of ambient air pollution and the relationship between air pollution levels and respiratory events is supra-linear. Wildfires and extreme weather events such as heat waves, which are becoming more common owing to climate change, are major threats to COPD patients and acutely increase their risk of morbidity and mortality. Exposure to air pollution also impairs lung growth in children and as such may lead to developmental COPD. GOLD recommends strong public health policies around the world to reduce ambient air pollution and for implementation of public warning systems and advisories, including where possible the use of personalised apps, to alert patients when ambient air pollution levels exceed acceptable minimal thresholds. When household particulate content exceeds acceptable thresholds, patients should consider using air cleaners and filters where feasible. Air pollution is a major health threat to patients living with COPD and actions are urgently required to reduce the morbidity and mortality related to poor air quality around the world.

The clinical and inflammatory relationships between periodontitis and chronic obstructive pulmonary disease

AIM

To investigate associations between periodontitis and chronic obstructive pulmonary disease (COPD) with and without alpha-1 antitrypsin deficiency (AATD), including neutrophil functions implicated in tissue damage.

METHODS

The presence and severity of periodontitis (using two international criteria) and lung disease were assessed in 156 COPD patients with and without AATD accounting for common confounding factors. Saliva and systemic inflammatory markers were measured by ELISA together with neutrophil migration.

RESULTS

COPD and AATD patients exhibited higher prevalence of periodontitis (COPD 95%; AATD 88%) than reported in unselected community-dwelling populations even when risk factors (age, smoking history, socio-economic status and dental habits) were considered. Periodontitis severity associated with lung disease severity (AATD, periodontitis versus no periodontitis; FEV1 = 56% versus 99% predicted; TLCO = 59% versus 81% predicted, p < .0001 for both). Neutrophil migratory accuracy declined in stage II-IV periodontitis patients with COPD or AATD compared to COPD or AATD with no or stage I periodontitis. Improved dental habits appeared to be associated with a reduction in exacerbation frequency in COPD.

CONCLUSION

The results support shared pathophysiology between periodontitis and COPD, especially when associated with AATD. This may reflect an amplification of neutrophilic inflammation and altered neutrophil functions, already described in periodontitis, COPD and AATD.

Neutrophil phenotypes in chronic lung disease

Introduction: Neutrophils are the most abundant inflammatory cells in the lungs of patients with chronic lung diseases, especially COPD, yet despite this, patients often experience repeated chest infections. Neutrophil function may be altered in disease, but the reasons are unclear. In chronic disease, sequential pro-inflammatory and pro-repair responses appear distorted. As understanding of neutrophil heterogeneity has expanded, it is suggested that different neutrophil phenotypes may impact on health and disease. Areas covered: In this review, the definition of cellular phenotype, the implication of neutrophil surface markers and functions in chronic lung disease and the complex influences of external, local and genetic factors on these changes are discussed. Literature was accessed up to the 19 July 2019 using: PubMed, US National Library of Medicine National Institutes of Health and the National Centre for Biotechnology Information. Expert opinion: As more is learned about neutrophils, the further we step from the classical view of neutrophils being unrefined killing machines to highly complex and finely tuned cells. Future therapeutics may aim to normalize neutrophil function, but to achieve this, knowledge of phenotypes in humans and how these relate to observed pathology and disease processes is required.

Model-based evaluation of the long-term cost-effectiveness of systematic case-finding for COPD in primary care

Introduction

‘One-off’ systematic case-finding for COPD using a respiratory screening questionnaire is more effective and cost-effective than routine care at identifying new cases. However, it is not known whether early diagnosis and treatment is beneficial in the longer term. We estimated the long-term cost-effectiveness of a regular case-finding programme in primary care.

Methods

A Markov decision analytic model was developed to compare the cost-effectiveness of a 3-yearly systematic case-finding programme targeted to ever smokers aged ≥50 years with the current routine diagnostic process in UK primary care. Patient-level data on case-finding pathways was obtained from a large randomised controlled trial. Information on the natural history of COPD and treatment effects was obtained from a linked COPD cohort, UK primary care database and published literature. The discounted lifetime cost per quality-adjusted life-year (QALY) gained was calculated from a health service perspective.

Results

The incremental cost-effectiveness ratio of systematic case-finding versus current care was £16 596 per additional QALY gained, with a 78% probability of cost-effectiveness at a £20 000 per QALY willingness-to-pay threshold. The base case result was robust to multiple one-way sensitivity analyses. The main drivers were response rate to the initial screening questionnaire and attendance rate for the confirmatory spirometry test.

Discussion

Regular systematic case-finding for COPD using a screening questionnaire in primary care is likely to be cost-effective in the long-term despite uncertainties in treatment effectiveness. Further knowledge of the natural history of case-found patients and the effectiveness of their management will improve confidence to implement such an approach.

Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Lung Disease: the GOLD science committee report 2019

Precision medicine is a patient-specific approach that integrates all relevant clinical, genetic and biological information in order to optimise the therapeutic benefit relative to the possibility of side-effects for each individual. Recent clinical trials have shown that higher blood eosinophil counts are associated with a greater efficacy of inhaled corticosteroids (ICSs) in chronic obstructive pulmonary disease (COPD) patients. Blood eosinophil counts are a biomarker with potential to be used in clinical practice, to help target ICS treatment with more precision in COPD patients with a history of exacerbations despite appropriate bronchodilator treatment.The Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2017 pharmacological treatment algorithms, based on the ABCD assessment, can be applied relatively easily to treatment-naive individuals at initial presentation. However, their use is more problematic during follow-up in patients who are already on maintenance treatment. There is a need for a different system to guide COPD pharmacological management during follow-up.Recent large randomised controlled trials have provided important new information concerning the therapeutic effects of ICSs and long-acting bronchodilators on exacerbations. The new evidence regarding blood eosinophils and inhaled treatments, and the need to distinguish between initial and follow-up pharmacological management, led to changes in the GOLD pharmacological treatment recommendations. This article explains the evidence and rationale for the GOLD 2019 pharmacological treatment recommendations.

Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Lung Disease 2017 Report. GOLD Executive Summary

This Executive Summary of the Global Strategy for the Diagnosis, Management, and Prevention of COPD, Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2017 report focuses primarily on the revised and novel parts of the document. The most significant changes include: (1) the assessment of chronic obstructive pulmonary disease has been refined to separate the spirometric assessment from symptom evaluation. ABCD groups are now proposed to be derived exclusively from patient symptoms and their history of exacerbations; (2) for each of the groups A to D, escalation strategies for pharmacologic treatments are proposed; (3) the concept of deescalation of therapy is introduced in the treatment assessment scheme; (4) nonpharmacologic therapies are comprehensively presented; and (5) the importance of comorbid conditions in managing chronic obstructive pulmonary disease is reviewed.

Global Strategy for the Diagnosis, Management and Prevention of Chronic Obstructive Lung Disease 2017 Report: GOLD Executive Summary

This Executive Summary of the Global Strategy for the Diagnosis, Management and Prevention of COPD, Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2017 Report focuses primarily on the revised and novel parts of the document. The most significant changes include: (i) the assessment of chronic obstructive pulmonary disease has been refined to separate the spirometric assessment from symptom evaluation. ABCD groups are now proposed to be derived exclusively from patient symptoms and their history of exacerbations; (ii) for each of the groups A to D, escalation strategies for pharmacological treatments are proposed; (iii) the concept of de-escalation of therapy is introduced in the treatment assessment scheme; (iv)non-pharmacological therapies are comprehensively presented and (v) the importance of co-morbid conditions in managing COPD is reviewed.

Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Lung Disease 2017 Report: GOLD Executive Summary

This Executive Summary of the Global Strategy for the Diagnosis, Management, and Prevention of COPD (GOLD) 2017 Report focuses primarily on the revised and novel parts of the document. The most significant changes include: 1) the assessment of COPD has been refined to separate the spirometric assessment from symptom evaluation. ABCD groups are now proposed to be derived exclusively from patient symptoms and their history of exacerbations; 2) for each of the groups A to D, escalation strategies for pharmacological treatments are proposed; 3) the concept of de-escalation of therapy is introduced in the treatment assessment scheme; 4) nonpharmacologic therapies are comprehensively presented and; 5) the importance of comorbid conditions in managing COPD is reviewed.

Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Lung Disease 2017 Report: GOLD Executive Summary

This Executive Summary of the Global Strategy for the Diagnosis, Management, and Prevention of COPD (GOLD) 2017 Report focuses primarily on the revised and novel parts of the document. The most significant changes include: 1) the assessment of chronic obstructive pulmonary disease has been refined to separate the spirometric assessment from symptom evaluation. ABCD groups are now proposed to be derived exclusively from patient symptoms and their history of exacerbations; 2) for each of the groups A to D, escalation strategies for pharmacological treatments are proposed; 3) the concept of de-escalation of therapy is introduced in the treatment assessment scheme; 4) nonpharmacologic therapies are comprehensively presented and; 5) the importance of comorbid conditions in managing COPD is reviewed.

Pathophysiology of Emphysema and Implications

This article serves as a CME-available, enduring material summary of the following COPD9_USA presentations: "Overview of Lung Injury in COPD: Types and Key Questions" Presenter: Caroline Owen, MD, PhD Emphysema as a Disease of Deficient Tissue Repair/Maintenance" Presenter: Rubin Tuder, MD.

A randomised, placebo-controlled study of the CXCR2 antagonist AZD5069 in bronchiectasis

This randomised double-blind placebo-controlled parallel-group multicentre phase IIa study evaluated the effect of the CXCR2 antagonist AZD5069 on sputum neutrophil counts in adults with bronchiectasis.Patients were randomised 1:1 to receive AZD5069 80 mg or placebo orally twice daily for 28 days. Assessments included blood cell counts, inflammatory markers in blood, morning spontaneous sputum, lung function, safety and tolerability and patients completed daily BronkoTest diary cards. The primary outcome measure was the change in absolute sputum neutrophil count.Of 52 randomised patients, 45 completed treatment, 20 (76.9%) out of 26 receiving AZD5069 and 25 (96.2%) out of 26 receiving placebo. AZD5069 reduced the absolute neutrophil cell count in morning sputum by 69% versus placebo (p=0.004); percentage sputum neutrophil count was reduced by 36% (p=0.008). The number of infections/exacerbations was similar with AZD5069 and placebo (nine versus eight), but these led to more study discontinuations with AZD5069 (four versus zero). Sputum interleukin (IL)-6 and growth-regulated oncogene (GRO)-α and serum GRO-α, IL-1ß and IL-8 levels increased with AZD5069 versus placebo (all p<0.001), while serum high-sensitivity C-reactive protein levels did not change. AZD5069 was well tolerated.AZD5069 markedly reduced absolute sputum neutrophil counts in bronchiectasis patients, although this was not associated with improvements in clinical outcomes in this exploratory study.

The COPD Biomarker Qualification Consortium (CBQC)

Knowledge about the pathogenesis and pathophysiology of chronic obstructive pulmonary disease (COPD) has advanced dramatically over the last 30 years. Unfortunately, this has had little impact in terms of new treatments. Over the same time frame, only one new class of medication for COPD has been introduced. Even worse, the rate at which new treatments are being developed is slowing. The development of new tools for the assessment of new treatments has not kept pace with understanding of the disease. In part, this is because drug development tools require a regulatory review, and no interested party has been in a position to undertake such a process. In order to facilitate the development of novel tools to assess new treatments, the Food and Drug Administration, in collaboration with the COPD Foundation, the National Heart Lung and Blood Institute and scientists from the pharmaceutical industry and academia conducted a workshop to survey the available information that could contribute to new tools. Based on this, a collaborative project, the COPD Biomarkers Qualification Consortium, was initiated. The Consortium in now actively preparing integrated data sets from existing resources that can address the problem of drug development tools for COPD.

Inflammatory mediators in spontaneously produced sputum

Airway inflammation is currently the subject of intense research interest concerning both the nature of the inflammatory cells, proteins, and cytokines present. These data are being used to define and assess the severity, cause, prognosis, and response to treatment of airway inflammatory disease. Spontaneous sputum is a useful method for studying inflammation in the larger airways, in diseases such as asthma, bronchitis, and bronchiectasis.

ANCA-associated vasculitis is linked to carriage of the Z allele of α₁ antitrypsin and its polymers

BACKGROUND

Small studies have linked α1 antitrypsin (α1AT) deficiency to patients with antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV).

OBJECTIVE

To test the validity and the mechanism of this association between α1AT and AAV.

METHODS

The distribution of α1AT deficiency alleles Z and S was compared between 856 White Europeans with AAV and 1505 geographic and ethnically matched healthy controls. Genotyping was performed by allelic discrimination assay.

RESULTS

were compared between cases and controls using χ(2) tests. The serum and renal biopsies for α1AT polymers were compared using the polymer-specific 2C1 antibody. The role of α1AT polymers in promoting inflammation was investigated by examining their ability to prime neutrophils for ANCA activation as assessed by CD62L shedding, superoxide production and myeloperoxidase degranulation. Results The Z but not the S allele was over-represented in the patients compared with controls (HR=2.25, 95% CI 1.60 to 3.19). Higher concentrations of polymers of α1AT were detected in serum from patients carrying the Z allele than in those not carrying the Z allele (median (IQR) 1.40 (0.91-3.32) mg/dl vs 0.17 (0.06-0.28) mg/dl, p<0.001); polymers of α1AT were also seen in the renal biopsy of a patient with vasculitic glomerulonephritis. Polymers of α1AT primed neutrophils with CD62L shedding and increased superoxide production following ANCA activation. Carriage of the Z allele was not associated with disease severity, survival or relapse.

CONCLUSIONS

The Z but not the S deficiency allele is associated with AAV. Polymers of α1AT are present in the serum and glomeruli of at least some patients with the Z allele, which may promote inflammation through priming of neutrophils.

Mechanisms of neutrophil transmigration across the vascular endothelium in COPD

Chronic obstructive pulmonary disease (COPD) is a common and important disease. Neutrophils have been shown to play a fundamental role in its development and progression. Understanding the mechanisms underlying the trafficking of neutrophils across the vascular endothelium into the lung could potentially allow the development of targeted biological treatments. The early stages of neutrophil tethering, adherence to and rolling on the endothelium have been determined. The later stages of diapedesis through the glycocalyx, endothelial cell (EC) layer and basement membrane, which are less well characterised, have been reviewed here. Evidence obtained from in vitro and in vivo work, concerning the implicated adhesion molecules on the neutrophil and endothelium, the mechanisms for neutrophil navigation through the EC junction (paracellular route) and evidence for transmigration through the body of an EC itself (transcellular route), is considered. The mechanisms are complex and are often disease and stimulus specific. There is evidence that a significant degree of redundancy occurs. Transmigration in the lung differs from that in other organs in that the neutrophil can exit the circulation either through the postcapillary venule in the systemic circulation or through the capillary in the pulmonary circulation. A number of factors make the mechanisms of transmigration within the lung and COPD model unique. These include physical differences between the flow through the capillary and the postcapillary venule, the modulating effect of the alveolar epithelium and other cells such as the macrophage, the presence of a 'diseased' neutrophil and indeed the presence or absence of acute, acute on chronic or chronic pulmonary disease.

Retinoid treatment of Emphysema in Patients on the Alpha-1 International Registry. The REPAIR study: study design, methodology and quality control of study assessments

Emphysema is characterized by the destruction of alveolar wall and enlargement of alveolar airspaces, resulting in a reduction of the total lung gas exchange area, loss of lung elastic recoil and hyperinflation. The REPAIR study (Retinoid treatment of Emphysema in Patients on the Alpha-1 International Registry) is the first proof-of-concept study of a new potential disease-modifying drug, Palovarotene©, an orally active, gamma selective retinoid agonist in patients with emphysema secondary to alpha-1-antitrypsin deficiency (AATD) as a model population for the general smoke-induced emphysema population. This article describes the study design as well as the effectiveness of the quality control that was implemented on the key efficacy endpoints, based on data derived from the placebo-treated subjects. In this multicentre, multinational study the implementation of standardized procedures included: careful site selection, use of trained staff, regular monitoring and machine calibration, use of biological controls and regular feedback to sites by an independent quality control centre. All of these procedures resulted in high-quality measurements of lung density, spirometry, static lung volumes and gas transfer. It was also confirmed that CT lung density was the most sensitive endpoint followed by TLco, FEV(1) and RV measured by body box.

Mortality in alpha-1-antitrypsin deficiency in the United Kingdom

BACKGROUND

Four hundred and eighty-eight PiZ alpha-1-antitrypsin deficient patients, who had joined the UK registry over a 9-year period, were followed in an observational study to determine mortality. None had received A1AT augmentation therapy.

METHODS

Cause of death was confirmed from death certification and medical records. Patients were censored according to length of time on the program or until they withdrew from the program.

RESULTS

There were 56 deaths of which 30 were attributed to respiratory causes. Of the remaining 26 deaths, 4 were due to complications from lung transplant, 6 due to liver disease (including 2 post-liver transplant) and the other 16 due to a variety of causes. Kaplan-Meier plots indicated a cumulative hazard for mortality of 18.1% in 9 years, correcting for time of follow up. When categorised for FEV1 percent-predicted, the group with severe impairment had increased mortality (p = <0.001) compared with the mild group and there was a direct relationship between severity and mortality. The severe group had increased mortality compared with the mild group when categorised for KCO percent-predicted (p<0.001), RV/TLC ratio (p<0.001) or emphysema score on CT scan (p<0.001 upper zone). Cox regression analyses indicated that these relationships remained when corrected for age. There were no differences in mortality after categorisation for educational level or occupational group.

CONCLUSION

Mortality in a cohort of A1AT deficient patients (PiZ phenotype) in the UK was 2% per year and was associated with lung function impairment and emphysema severity on CT scan, but not social status.

Outcomes for COPD pharmacological trials: from lung function to biomarkers

The American Thoracic Society/European Respiratory Society jointly created a Task Force on "Outcomes for COPD pharmacological trials: from lung function to biomarkers" to inform the chronic obstructive pulmonary disease research community about the possible use and limitations of current outcomes and markers when evaluating the impact of a pharmacological therapy. Based on their review of the published literature, the following document has been prepared with individual sections that address specific outcomes and markers, and a final section that summarises their recommendations.

A polymorphism of the alpha1-antitrypsin gene represents a risk factor for liver disease

Alpha(1)-antitrypsin deficiency (AATD) due to homozygosity of the protease inhibitor (Pi) Z variant predisposes to childhood liver disease and pulmonary emphysema. About 10% of all neonates with AATD develop liver disease, and about 3% overall progress to severe disease. AATD is a principal genetic indication for liver transplantation in children. The liver pathology is associated with accumulation of abnormally folded protein in hepatocytes, the principal producers of circulating alpha(1)-antitrypsin (AAT). It is currently unknown why only a small proportion of Pi ZZ individuals progress to clinically significant cirrhosis. The AAT gene shows significant variation, and we hypothesized that cryptic genetic variants within the AAT gene may contribute to susceptibility to liver disease. In a case-control study consisting of 42 patients with established moderate-to-severe liver disease and 335 homozygous Pi ZZ patients who mostly presented with chronic obstructive pulmonary disease (n = 322: 242 index cases and 80 unaffected sibs) or were asymptomatic (n = 13) with no evidence of liver disease, we identified a single nucleotide polymorphism (SNP) that conferred a significant risk for liver disease (P = 0.007). The frequency of the SNP was no different in 242 Pi ZZ cases with chronic obstructive pulmonary disease compared with 80 nonindex cases. The SNP therefore appears to confer susceptibility to liver disease, although reporter gene assays failed to show any functional differences between alleles.

CONCLUSION

This is the first description of a genetic modifier of liver disease in homozygous ZZ children and has potential implications for screening and possible therapies that are currently being developed.

Investigating new standards for prophylaxis in reduction of exacerbations--the INSPIRE study methodology

Bronchodilators, including long-acting beta(2)-adrenoceptor agonists and anticholinergic bronchodilators, are effective in the treatment of chronic obstructive pulmonary disease. Evidence suggests that the addition of a long-acting beta(2)-agonist to an inhaled corticosteroid is associated with a reduced rate of exacerbations compared with either treatment alone or placebo. However, it is not known whether a long-acting beta(2)-agonist/inhaled corticosteroid combination is more effective than an anticholinergic bronchodilator alone in reducing exacerbations. The Investigating New Standards for Prophylaxis In Reduction of Exacerbations (INSPIRE) trial will study salmeterol (a long-acting beta(2)-agonist) in combination with fluticasone propionate (an inhaled corticosteroid) compared with tiotropium bromide (an anticholinergic bronchodilator) in patients with moderate-to-severe chronic obstructive pulmonary disease. The INSPIRE study is a multicentre, randomised, double-blind, double dummy, parallel group study conducted over 104 weeks. This is the first study to use two parallel definitions of an exacerbation; an event-based exacerbation is defined as one that requires use of healthcare resources, including additional treatment and hospitalization, whereas a symptom-based exacerbation is defined as one that satisfies the 1987 Anthonisen criteria. It is also the first study to compare the long-term effects of salmeterol/fluticasone propionate with tiotropium bromide on the rate of event-based exacerbations. Endpoints include rate of exacerbations (primary endpoint), time to first exacerbation, and duration of exacerbations. Health outcomes will be assessed via the St George's Respiratory Questionnaire. If the innovative methodology of utilizing 2 definitions of exacerbation proves successful, it will set the benchmark for future studies in chronic obstructive pulmonary disease.

Comparison of the bioavailabilities and anticoagulant activities of two warfarin formulations

Changes in the British Pharmacopoeia dissolution time requirements have necessitated reformulation of warfarin sodium ('Marevan'). The old and new formulations were compared with each other in eight healthy volunteers given a single 15 mg dose of each in a cross-over study and also in 19 patients receiving warfarin therapy. In the volunteer study, a significant but small increase in bioavailability was observed for the new formulation. However, the effects of the two formulations on the prothrombin ratio and on clotting factors II, VII, IX and X were not significantly different. Irrespective of formulation, the greatest changes in factors II, VII and X were observed after the first dose of warfarin. With factor IX, the greatest response was observed after the second dose. The clinical study in patients confirmed that the old and new formulations of Marevan are interchangeable on a dose for dose basis. A sensitive semi-automated warfarin assay technique is described.