Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study

INTRODUCTION

The multiorgan impact of moderate to severe coronavirus infections in the post-acute phase is still poorly understood. We aimed to evaluate the excess burden of multiorgan abnormalities after hospitalisation with COVID-19, evaluate their determinants, and explore associations with patient-related outcome measures.

METHODS

In a prospective, UK-wide, multicentre MRI follow-up study (C-MORE), adults (aged ≥18 years) discharged from hospital following COVID-19 who were included in Tier 2 of the Post-hospitalisation COVID-19 study (PHOSP-COVID) and contemporary controls with no evidence of previous COVID-19 (SARS-CoV-2 nucleocapsid antibody negative) underwent multiorgan MRI (lungs, heart, brain, liver, and kidneys) with quantitative and qualitative assessment of images and clinical adjudication when relevant. Individuals with end-stage renal failure or contraindications to MRI were excluded. Participants also underwent detailed recording of symptoms, and physiological and biochemical tests. The primary outcome was the excess burden of multiorgan abnormalities (two or more organs) relative to controls, with further adjustments for potential confounders. The C-MORE study is ongoing and is registered with ClinicalTrials.gov, NCT04510025.

FINDINGS

Of 2710 participants in Tier 2 of PHOSP-COVID, 531 were recruited across 13 UK-wide C-MORE sites. After exclusions, 259 C-MORE patients (mean age 57 years [SD 12]; 158 [61%] male and 101 [39%] female) who were discharged from hospital with PCR-confirmed or clinically diagnosed COVID-19 between March 1, 2020, and Nov 1, 2021, and 52 non-COVID-19 controls from the community (mean age 49 years [SD 14]; 30 [58%] male and 22 [42%] female) were included in the analysis. Patients were assessed at a median of 5·0 months (IQR 4·2-6·3) after hospital discharge. Compared with non-COVID-19 controls, patients were older, living with more obesity, and had more comorbidities. Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p<0·0001) and independently associated with COVID-19 status (odds ratio [OR] 2·9 [95% CI 1·5-5·8]; padjusted=0·0023) after adjusting for relevant confounders. Compared with controls, patients were more likely to have MRI evidence of lung abnormalities (p=0·0001; parenchymal abnormalities), brain abnormalities (p<0·0001; more white matter hyperintensities and regional brain volume reduction), and kidney abnormalities (p=0·014; lower medullary T1 and loss of corticomedullary differentiation), whereas cardiac and liver MRI abnormalities were similar between patients and controls. Patients with multiorgan abnormalities were older (difference in mean age 7 years [95% CI 4-10]; mean age of 59·8 years [SD 11·7] with multiorgan abnormalities vs mean age of 52·8 years [11·9] without multiorgan abnormalities; p<0·0001), more likely to have three or more comorbidities (OR 2·47 [1·32-4·82]; padjusted=0·0059), and more likely to have a more severe acute infection (acute CRP >5mg/L, OR 3·55 [1·23-11·88]; padjusted=0·025) than those without multiorgan abnormalities. Presence of lung MRI abnormalities was associated with a two-fold higher risk of chest tightness, and multiorgan MRI abnormalities were associated with severe and very severe persistent physical and mental health impairment (PHOSP-COVID symptom clusters) after hospitalisation.

INTERPRETATION

After hospitalisation for COVID-19, people are at risk of multiorgan abnormalities in the medium term. Our findings emphasise the need for proactive multidisciplinary care pathways, with the potential for imaging to guide surveillance frequency and therapeutic stratification.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

AB0424 A RANDOMIZED, DOUBLE-BLIND, PLACEBO CONTROLLED STUDY OF THE SAFETY, TOLERABILITY, PHARMACOKINETICS, AND PHARMACODYNAMICS OF ALPN-303, A POTENT DUAL BAFF/APRIL INHIBITOR, IN ADULT HEALTHY VOLUNTEERS

Background

Therapeutic agents targeting the B-cell cytokines BAFF and/or APRIL, including the wild-type (WT) TACI-Fc fusion proteins atacicept and telitacicept, have demonstrated promising clinical potential in rheumatic diseases like systemic lupus erythematosus (SLE) and/or other B-cell-related diseases such as autoantibody-related nephritides. ALPN-303 is an Fc fusion protein of a variant, engineered TACI domain which mediates significantly more potent inhibitory activity in vitro as compared to WT TACI-Fc or BAFF- or APRIL-specific monoclonal antibodies, along with enhanced pharmacokinetic (PK) and immunomodulatory properties in preclinical studies1,2. ALPN-303 may therefore significantly improve clinical outcomes in SLE and other B-cell-related diseases.

Objectives

To evaluate the safety, tolerability, PK, and pharmacodynamics (PD) of ALPN-303 in adult healthy volunteers (HV).

Methods

In this first-in-human study (NCT05034484), adult HVs are enrolled in single ascending dose cohorts of intravenously (IV) or subcutaneously (SC) administered ALPN-303. For each IV cohort, the first 2 subjects are randomized 1:1 to receive ALPN-303 or placebo, followed by the remaining 4 subjects randomized 3:1 to receive ALPN-303 or placebo. For each SC cohort, HVs are randomized 4:2 to receive a single SC dose of ALPN-303 or placebo. All subjects are followed to assess safety and PK of ALPN-303, to measure levels of circulating immunoglobulins (Ig), and to characterize leukocyte populations in peripheral blood by flow cytometry.

Results

ALPN-303 has been well tolerated and overall exhibits dose-dependent PK and expected PD effects on circulating Ig levels. Dose escalation is expected to be completed by the time of the meeting; the presentation will include all available safety, PK, and PD (circulating Ig and B-cell population) data.

Conclusion

In this first-in-human study, ALPN-303 demonstrates acceptable preliminary safety and tolerability, and exhibits expected PD effects on circulating Ig and B-cell populations. These findings support future clinical development of ALPN-303 in patients with SLE or other B-cell-mediated diseases.

References

[1]Dillon SR, Evans LS, Lewis KE, et al. OP0039 ALPN-303, an enhanced, potent dual BAFF/APRIL antagonist engineered by directed evolution for the treatment of systemic lupus erythematosus (SLE) and other B cell related autoimmune diseases. Annals of the Rheumatic Diseases 2021;80:21.

[2]Dillon SR, Evans LS, Lewis KE, et al. ALPN-303, an enhanced, potent dual BAFF/APRIL antagonist engineered by directed evolution for the treatment of systemic lupus erythematosus (SLE) and other B cell-related diseases. Arthritis Rheumatol. 2021; 73 (suppl 10).

Disclosure of Interests

Pille Harrison Employee of: Alpine Immune Sciences Inc, Jason Lickliter Consultant of: ENA Oncology and Amplia. Neither of these were developing drugs for rheumatological diseases., Stacey R. Dillon Employee of: Alpine Immune Sciences Inc, Kristi Manjarrez Employee of: Alpine Immune Sciences Inc, Alina Smith Employee of: Alpine Immune Sciences Inc, Melody Dossey Employee of: Alpine Immune Sciences Inc, Lori Blanchfield Employee of: Alpine Immune Sciences Inc, Allison Chunyk Employee of: Alpine Immune Sciences Inc, Hany Zayed Employee of: Alpine Immune Sciences Inc, Stanford L. Peng Employee of: Alpine Immune Sciences Inc

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

Dysregulation of the actin scavenging system and inhibition of DNase activity following severe thermal injury

Background

Circulating cell‐free DNA (cfDNA) is not found in healthy subjects, but is readily detected after thermal injury and may contribute to the risk of multiple organ failure. The hypothesis was that a postburn reduction in DNase protein/enzyme activity could contribute to the increase in cfDNA following thermal injury.

Methods

Patients with severe burns covering at least 15 per cent of total body surface area were recruited to a prospective cohort study within 24 h of injury. Blood samples were collected from the day of injury for 12 months.

Results

Analysis of blood samples from 64 patients revealed a significant reduction in DNase activity on days 1–28 after injury, compared with healthy controls. DNase protein levels were not affected, suggesting the presence of an enzyme inhibitor. Further analysis revealed that actin (an inhibitor of DNase) was present in serum samples from patients but not those from controls, and concentrations of the actin scavenging proteins gelsolin and vitamin D‐binding protein were significantly reduced after burn injury. In a pilot study of ten military patients with polytrauma, administration of blood products resulted in an increase in DNase activity and gelsolin levels.

Conclusion

The results of this study suggest a novel biological mechanism for the accumulation of cfDNA following thermal injury by which high levels of actin released by damaged tissue cause a reduction in DNase activity. Restoration of the actin scavenging system could therefore restore DNase activity, and reduce the risk of cfDNA‐induced host tissue damage and thrombosis.

3 Platelet rich plasma for acute achilles tendon rupture: a double-blind, multicentre, randomised, placebo-controlled trial

Aim

Slow recovery and disability after Achilles tendon rupture are major challenges. Platelet Rich Plasma (PRP) is an autologous supraphysiological concentration of platelets from whole blood that has demonstrated positive cellular and physiological effects on healing in the laboratory and is widely used in musculoskeletal treatments. However, evidence from adequately powered, robust clinical trials is lacking. We aimed to determine the clinical efficacy of PRP for treatment of acute Achilles tendon rupture.

Methods

230 adults starting Achilles rupture non-surgical management within 12 days of injury were randomised to PRP injection or dry needle insertion to the rupture gap, under local anaesthetic. Participants were blinded to study treatment and received standardised rehabilitation. Blinded outcome assessments were at 4, 7, 13, and 24 weeks. The primary outcome was muscle-tendon function assessed by work performed during the heel-rise endurance test (HRET), measured with the Limb Symmetry Index (LSI) (0–100%; 100% denotes full recovery) at 24 weeks. Secondary outcomes were the Achilles Tendon Rupture Score (ATRS), quality of life (SF-12), pain and goal attainment. The trial was prospectively registered.

Results

Of 230 participants, 114 were allocated to PRP injection (103 received PRP), 116 were allocated to and received placebo. At 24 weeks, 201/230 (87%) completed the HRET and 214/230 (93%) completed patient reported outcomes. Participant characteristics between the groups were similar. There was no difference between groups at 24 weeks in LSI (mean difference = -4.373; 95% CI −11.217 to 2.471; p=0.195). There were no differences in the secondary outcomes and adverse event rates.

Conclusion

This trial design and standardised PRP preparation secure the first robust clinical trial evidence for PRP in managing Achilles tendon rupture, and suggest that PRP offers no patient benefit. The use of PRP in soft tissue injuries must be questionable unless supported by equally robust evidence indicating positive outcomes.

The use of platelets in regenerative medicine and proposal for a new classification system: guidance from the SSC of the ISTH

Autologous and single-donor allogenic platelet preparations are increasingly being used in many areas of regenerative medicine. However, there are few properly controlled randomized clinical trials, and the preparation, content and characteristics of platelet preparations are generally poorly defined and controlled. The Platelet Physiology Subcommittee of the Scientific and Standardization Committee (SSC) of the ISTH formed a working party of experts with the aim of producing consensus recommendations for guidance on the use of platelets in regenerative medicine. Owing to a lack of investigations that provide definitive evidence for the efficacy, definition and use of different platelet preparations in regenerative medicine, there were insufficient data to develop evidence-based guidelines. Therefore, the RAND method was used, which obtains a formal consensus among experts particularly when scientific evidence is absent, scarce and/or heterogeneous. Using this approach, each expert scored as 'appropriate', 'uncertain' or 'inappropriate' a series of 45 statements about the practice of regenerative medicine with platelets, which included different sections on general aspects, platelet preparations, clinical trial design, and potential utility in different clinical scenarios. After presentation and public discussion at SSC meetings, the assessments were further refined to produce final consensus recommendations, which constitute the subject of the present report.

Wrinkling in engineering fabrics: a comparison between two different comprehensive modelling approaches

We consider two 'comprehensive' modelling approaches for engineering fabrics. We distinguish the two approaches using the terms 'semi-discrete' and 'continuum', reflecting their natures. We demonstrate a fitting procedure, used to identify the constitutive parameters of the continuum model from predictions of the semi-discrete model, the parameters of which are in turn fitted to experimental data. We, then, check the effectiveness of the continuum model by verifying the correspondence between semi-discrete and continuum model predictions using test cases not previously used in the identification process. Predictions of both modelling approaches are compared against full-field experimental kinematic data, obtained using stereoscopic digital image correlation techniques, and also with measured force data. Being a reduced order model and being implemented in an implicit rather than an explicit finite-element code, the continuum model requires significantly less computational power than the semi-discrete model and could therefore be used to more efficiently explore the mechanical response of engineering fabrics.

Successful endoscopic management of a persistent bronchobiliary fistula with Histoacryl®/Lipiodol® mixture

Introduction A bronchobiliary fistula (BBF) following liver directed therapy (resection/ablation) is a rare complication in which an abnormal communication between the biliary tract and bronchial tree is formed. This case report describes the successful management of a persistent BBF following multiple liver wedge resections and microwave ablation in a patient with a metastatic neuroendocrine tumour of the terminal ileum. Case history A 69-year-old man presented with unexplained weight loss and was subsequently diagnosed with a neuroendocrine tumour of the terminal ileum and liver metastasis. Following elective right hemicolectomy and multiple bilobar liver wedge resections combined with liver microwave ablation, he developed an early bile leak. A month later, a right subphrenic collection was identified and four months following surgery, biloptysis was noted. Numerous attempts with endoscopic retrograde biliary drainage (ERBD) failed to achieve sufficient drainage. The patient was treated successfully with endoscopic injection of a mixture of Histoacryl® glue (B Braun, Sheffield, UK) and Lipiodol® (Guerbet, Solihull, UK). There was no evidence of the BBF one year following intervention. Conclusions This novel approach for persistent BBF management using endoscopic Histoacryl® glue embolisation of the fistula tract should be considered either as an adjunct to ERBD or when biliary tract decompression by drainage and/or sphincterotomy fails, prior to proceeding with surgical interventions.

Chronic Muscle Contraction Headache: The Importance of Depression and Anxiety

Seventy consecutive patients presenting with a clinical diagnosis of chronic muscle contraction headache over a two-year period were evaluated for depression and anxiety scores, along with other possible aetiological factors in this form of headache. Fifty-five of these patients (33 from a hospital neurology clinic and 22 from a local general practice) completed a double-blind study to evaluate flupenthixol 0.5 mg twice daily, diazepam 5 mg twice daily and placebo as prophylactic agents.

Patients evaluated in the hospital neurology clinic had more frequent headaches of longer duration, higher analgesic consumption and higher depression, but no higher anxiety scores than those in general practice. Flupenthixol and diazepam were both significantly superior to placebo in reducing headaches and analgesic consumption. The trend was for flupenthixol to be superior to diazepam without reaching statistical significance. Flupenthixol was significantly better than diazepam and placebo in the reduction of Hamilton depression scores. This effect was independent of the effect on headache and analgesic reduction.

Atherothrombosis and Thromboembolism: Position Paper from the Second Maastricht Consensus Conference on Thrombosis

Atherothrombosis is a leading cause of cardiovascular mortality and long-term morbidity. Platelets and coagulation proteases, interacting with circulating cells and in different vascular beds, modify several complex pathologies including atherosclerosis. In the second Maastricht Consensus Conference on Thrombosis, this theme was addressed by diverse scientists from bench to bedside. All presentations were discussed with audience members and the results of these discussions were incorporated in the final document that presents a state-of-the-art reflection of expert opinions and consensus recommendations regarding the following five topics: 1. Risk factors, biomarkers and plaque instability: In atherothrombosis research, more focus on the contribution of specific risk factors like ectopic fat needs to be considered; definitions of atherothrombosis are important distinguishing different phases of disease, including plaque (in)stability; proteomic and metabolomics data are to be added to genetic information. 2. Circulating cells including platelets and atherothrombosis: Mechanisms of leukocyte and macrophage plasticity, migration, and transformation in murine atherosclerosis need to be considered; disease mechanism-based biomarkers need to be identified; experimental systems are needed that incorporate whole-blood flow to understand how red blood cells influence thrombus formation and stability; knowledge on platelet heterogeneity and priming conditions needs to be translated toward the in vivo situation. 3. Coagulation proteases, fibrin(ogen) and thrombus formation: The role of factor (F) XI in thrombosis including the lower margins of this factor related to safe and effective antithrombotic therapy needs to be established; FXI is a key regulator in linking platelets, thrombin generation, and inflammatory mechanisms in a renin-angiotensin dependent manner; however, the impact on thrombin-dependent PAR signaling needs further study; the fundamental mechanisms in FXIII biology and biochemistry and its impact on thrombus biophysical characteristics need to be explored; the interactions of red cells and fibrin formation and its consequences for thrombus formation and lysis need to be addressed. Platelet-fibrin interactions are pivotal determinants of clot formation and stability with potential therapeutic consequences. 4. Preventive and acute treatment of atherothrombosis and arterial embolism; novel ways and tailoring? The role of protease-activated receptor (PAR)-4 vis à vis PAR-1 as target for antithrombotic therapy merits study; ongoing trials on platelet function test-based antiplatelet therapy adjustment support development of practically feasible tests; risk scores for patients with atrial fibrillation need refinement, taking new biomarkers including coagulation into account; risk scores that consider organ system differences in bleeding may have added value; all forms of oral anticoagulant treatment require better organization, including education and emergency access; laboratory testing still needs rapidly available sensitive tests with short turnaround time. 5. Pleiotropy of coagulation proteases, thrombus resolution and ischaemia-reperfusion: Biobanks specifically for thrombus storage and analysis are needed; further studies on novel modified activated protein C-based agents are required including its cytoprotective properties; new avenues for optimizing treatment of patients with ischaemic stroke are needed, also including novel agents that modify fibrinolytic activity (aimed at plasminogen activator inhibitor-1 and thrombin activatable fibrinolysis inhibitor.

Assessment of platelet function in the laboratory

Platelet function testing is essential for the diagnosis of congenital/acquired bleeding disorders and may be useful for the prediction of surgical bleeding. Nowadays there is also much interest in monitoring the efficacy of anti-platelet therapy and measuring platelet hyper-function. However, this often presents clinical laboratories with significant challenges as platelet function tests are complex, poorly standardized, time consuming and quality assurance is not straightforward. There are also few comprehensive modern guidelines available and many recent published surveys have revealed poor standardization between laboratories.

Up until the late 1980’s the traditional clinical platelet function tests that were available were the bleeding time (BT), light transmission (LTA) and whole blood aggregometry (WBA) and various biochemical assays. These were also usually performed within specialized research and clinical laboratories. Since the last BCSH guidelines were published in 1988 a variety of new platelet function tests have become available. These include flow cytometry and an ever increasing choice of new commercial instruments. Although the potential clinical utility of the new assays is emerging some have not yet entered into routine clinical practice. It is encouraging that a number of standardization committees (e. g. CLSI, BCSH and ISTH Platelet Physiology SSC) are now beginning to produce new platelet function testing guidelines and this will hopefully improve clinical practice, quality assurance and result in less variability between different laboratories.

Comparison of multiple electrode aggregometry with lumi-aggregometry for the diagnosis of patients with mild bleeding disorders

Essentials There is a clinical need for new technologies to measure platelet function in whole blood. Mild bleeding disorders were evaluated using multiple electrode aggregometry (MEA). MEA is insensitive at detecting patients with mild platelet function and secretion defects. More studies are required to investigate MEA in patients with a defined set of platelet disorders.

SUMMARY

Background Multiple electrode aggregometry (MEA) measures changes in electrical impedance caused by platelet aggregation in whole blood. This approach is faster, more convenient and offers the advantage over light transmission aggregometry (LTA) of assessing platelet function in whole blood and reducing preanalytical errors associated with preparation of platelet-rich plasma (PRP). Several studies indicate the utility of this method in assessing platelet inhibition in individuals taking antiplatelet agents (e.g. aspirin and clopidogrel). Objective Our current study sought to evaluate the ability of MEA in diagnosing patients with mild bleeding disorders by comparison with light transmission lumi-aggregometry (lumi-LTA). Methods Forty healthy subjects and 109 patients with a clinical diagnosis of a mild bleeding disorder were recruited into the UK Genotyping and Phenotyping of Platelets study (GAPP, ISRCTN 77951167). MEA was performed on whole blood using one or two concentrations of ADP, PAR-1 peptide, arachidonic acid and collagen. Lumi-LTA was performed in PRP using several concentrations of ADP, adrenaline, arachidonic acid, collagen, PAR-1 peptide and ristocetin. Results Of 109 patients tested, 54 (49%) patients gave abnormal responses by lumi-LTA to one or more agonists. In contrast, only 16 (15%) patients were shown to have abnormal responses to one or more agonists by MEA. Conclusions In this study we showed that MEA is less sensitive in identifying patients with abnormal platelet function relative to lumi-LTA.

Local and Plasma Biomarker Profiles in Localized Aggressive Periodontitis

Localized aggressive periodontitis (LAP) patients possess a systemic hyperinflammatory response after lipopolysaccharide stimulation. However, the levels of inflammatory and bone biomarkers in plasma, as well as possible associations between local and plasma biomarkers, are unknown in LAP. This cross-sectional study aimed to characterize gingival crevicular fluid (GCF) and plasma biomarker profiles in LAP patients, their healthy siblings (HS), and healthy unrelated controls (HC). Fifty-eight LAP subjects, 33 HS, and 49 HC (African Americans, aged 5 to 25 y) were included. Following collection of clinical parameters with GCF and plasma samples, levels of 16 inflammatory and bone resorption biomarkers were determined with Milliplex. Univariate and correlation analyses were performed among all clinical and laboratorial parameters. Discriminant analyses were used to investigate groups of biomarkers discriminating LAP from HS and HC in GCF and plasma. GCF levels of multiple cytokines and chemokines and RANKL:OPG ratio (receptor activator of nuclear factor kappa-B ligand:osteoprotegerin) were higher in LAP disease, most of which positively correlated with probing depth and attachment loss of sampled sites. A group of IL-12p40, IL-6, IL-12p70, IL-2, and MIP-1α discriminated LAP diseased sites from twheir healthy sites, as well as from HS and HC healthy sites. In plasma, only RANKL levels were increased in LAP versus controls, which positively correlated with the percentage of affected sites and deep/bleeding sites. A plasma inflammatory profile including MIP-1α, IL-8, IL-10, and INF-γ could significantly discriminate LAP patients from HS and HC. No correlations were found between GCF and plasma levels of biomarkers. In conclusion, an inflammatory profile including groups of specific biomarkers in GCF and plasma may significantly discriminate LAP from healthy individuals. The hyperinflammatory response previously found in the peripheral blood of LAP patients is dependent on lipopolysaccharide stimulation, apparently resulting mostly in local tissue destruction and changes in biomarker profile, with a slight influence in the systemic inflammatory profile (ClinicalTrials.gov NCT01330719). Knowledge Transfer Statement: The results of this study can be possibly used by clinicians in the future as diagnostic tools for localized aggressive periodontitis. Thus, in the future, with proper consideration of cost, patient preference, chair-side feasibility and ultimately further studies validating the role of GCF markers for disease progression and response to treatment, this information could lead to more appropriate therapeutic decisions and the development of preventive approaches for susceptible patients.

Aggregatibacter actinomycetemcomitans in African Americans with Localized Aggressive Periodontitis

This study aims to investigate the prevalence of the highly leukotoxic JP2 sequence versus the minimally leukotoxic non-JP2 sequence of Aggregatibacter actinomycetemcomitans within a cohort of 180 young African Americans, with and without localized aggressive periodontitis (LAP), in north Florida. The study included patients aged 5 to 25 y: 60 LAP patients, 60 healthy siblings (HS), and 60 unrelated healthy controls (HC). Subgingival plaque was collected from LAP sites-diseased (PD ≥5 mm with bleeding on probing) and healthy (PD ≤3 mm with no bleeding on probing)-and from healthy sites of HS and HC. Plaque DNA was extracted and analyzed by polymerase chain reaction for the detection of the JP2 and non-JP2 sequences of A. actinomycetemcomitans. Overall, 90 (50%) subjects tested positive for the JP2 sequence. Fifty (83.33%) LAP subjects were carriers of the highly leukotoxic JP2 sequence, detected in 45 (75%) diseased sites and 34 (56.67%) healthy sites. Additionally, JP2 carriage was found in 16 HS (26.67%) and 24 HC (40%; P < 0.0001, among groups). The non-JP2 sequence was detected in 26 (14.44%) total subjects: 17 (28.33%) LAP patients detected in equal amounts of diseased and healthy sites (n = 11, 18.33%), 6 (10%) HS sites, and 3 (5%) HC sites (P < 0.05, among groups). The JP2 sequence was strongly associated with LAP-diseased sites in young African Americans, significantly more so than the non-JP2 (ClinicalTrials.gov NCT01330719). Knowledge Transfer Statement: Clinicians may use the results of this study to identify susceptible individuals to aggressive periodontitis, potentially leading to more appropriate selection of therapeutic choices.

Platelet responses to agonists in a cohort of highly characterised platelet donors are consistent over time

BACKGROUND AND OBJECTIVES

Platelet function shows significant inheritance that is at least partially genetically controlled. There is also evidence that the platelet response is stable over time, but there are few studies that have assessed consistency of platelet function over months and years. We aimed to measure platelet function in platelet donors over time in individuals selected from a cohort of 956 donors whose platelet function had been previously characterised.

MATERIALS AND METHODS

Platelet function was assessed by flow cytometry, measuring fibrinogen binding and P-selectin expression after stimulation with either cross-linked collagen-related peptide or adenosine 5'-diphosphate. Eighty-nine donors from the Cambridge Platelet Function Cohort whose platelet responses were initially within the lower or upper decile of reactivity were retested between 4 months and five and a half years later.

RESULTS

There was moderate-to-high correlation between the initial and repeat platelet function results for all assays (P ≤ 0·007, r² 0·2961-0·7625); furthermore, the range of results observed in the initial low and high responder groups remained significantly different at the time of the second test (P ≤ 0·0005).

CONCLUSION

Platelet function remains consistent over time. This implies that this potential influence on quality of donated platelet concentrates will remain essentially constant for a given donor.

Filgotinib (GLPG0634/GS-6034), an oral JAK1 selective inhibitor, is effective in combination with methotrexate (MTX) in patients with active rheumatoid arthritis and insufficient response to MTX: results from a randomised, dose-finding study (DARWIN 1)

OBJECTIVES

To evaluate the efficacy and safety of different doses and regimens of filgotinib, an oral Janus kinase 1 inhibitor, as add-on treatment to methotrexate (MTX) in patients with active rheumatoid arthritis (RA) and inadequate response to MTX.

METHODS

In this 24-week phase IIb study, patients with moderate-to-severe active RA receiving a stable dose of MTX were randomised (1:1:1:1:1:1:1) to receive placebo or 50, 100 or 200 mg filgotinib, administered once daily or twice daily. Primary end point was the percentage of patients achieving a week 12 American College of Rheumatology (ACR)20 response.

RESULTS

Overall, 594 patients were randomised and treated. At week 12, significantly more patients receiving filgotinib 100 mg once daily or 200 mg daily (both regimens) achieved an ACR20 response versus placebo. For other key end points at week 12 (ACR50, ACR-N, Disease Activity Score based on 28 joints and C reactive protein value, Clinical Disease Activity Index, Simplified Disease Activity Index and Health Assessment Questionnaire-Disability Index), differences in favour of 100  or 200 mg filgotinib daily were seen versus placebo; responses were maintained or improved through to week 24. Rapid onset of action and dose-dependent responses were observed for most efficacy end points and were associated with an increased haemoglobin concentration. No significant differences between once-daily and twice-daily regimens were seen. Treatment-emergent adverse event rates were similar in placebo and filgotinib groups. Serious infections occurred in one and five patients in the placebo and filgotinib groups, respectively. No tuberculosis or opportunistic infections were reported.

CONCLUSIONS

Filgotinib as add-on to MTX improved the signs and symptoms of active RA over 24 weeks and was associated with a rapid onset of action. Filgotinib was generally well tolerated.

TRIAL REGISTRATION NUMBER

NCT01888874.

Filgotinib (GLPG0634/GS-6034), an oral selective JAK1 inhibitor, is effective as monotherapy in patients with active rheumatoid arthritis: results from a randomised, dose-finding study (DARWIN 2)

Objectives

To evaluate the efficacy and safety of different doses of filgotinib, an oral Janus kinase 1 inhibitor, as monotherapy in patients with active rheumatoid arthritis (RA) and previous inadequate response to methotrexate (MTX).

Methods

In this 24-week phase IIb study, patients with moderately to severely active RA were randomised (1:1:1:1) to receive 50, 100 or 200 mg filgotinib once daily, or placebo, after a ≥4-week washout from MTX. The primary end point was the percentage of patients achieving an American College of Rheumatology (ACR)20 response at week 12.

Results

Overall, 283 patients were randomised and treated. At week 12, significantly more patients receiving filgotinib at any dose achieved ACR20 responses versus placebo (≥65% vs 29%, p<0.001). For other key end points at week 12 (ACR50, ACR70, ACR-N, Disease Activity Score based on 28 joints and C reactive protein, Clinical Disease Activity Index, Simplified Disease Activity Index and Health Assessment Questionnaire-Disability Index) significant differences from baseline in favour of filgotinib 100 and 200 mg versus placebo were seen; responses were maintained or improved through week 24. Rapid onset of action was observed for most efficacy end points. Dose-dependent increases in haemoglobin were observed. The percentage of patients with treatment-emergent adverse events (TEAE) was similar in the placebo and filgotinib groups (∼40%). Eight patients on filgotinib and one on placebo had a serious TEAE, and four patients, all of whom received filgotinib, experienced a serious infection. No tuberculosis or opportunistic infections were reported.

Conclusions

Over 24 weeks, filgotinib as monotherapy was efficacious in treating the signs and symptoms of active RA, with a rapid onset of action. Filgotinib was generally well tolerated.

Trial registration number

NCT01894516.

Initiating and imaging the coherent surface dynamics of charge carriers in real space

The tip of a scanning tunnelling microscope is an atomic-scale source of electrons and holes. As the injected charge spreads out, it can induce adsorbed molecules to react. By comparing large-scale 'before' and 'after' images of an adsorbate covered surface, the spatial extent of the nonlocal manipulation is revealed. Here, we measure the nonlocal manipulation of toluene molecules on the Si(111)-7 × 7 surface at room temperature. Both the range and probability of nonlocal manipulation have a voltage dependence. A region within 5-15 nm of the injection site shows a marked reduction in manipulation. We propose that this region marks the extent of the initial coherent (that is, ballistic) time-dependent evolution of the injected charge carrier. Using scanning tunnelling spectroscopy, we develop a model of this time-dependent expansion of the initially localized hole wavepacket within a particular surface state and deduce a quantum coherence (ballistic) lifetime of ∼10 fs.

Anion replacement at Au(110)/electrolyte interfaces

A characteristic reflection anisotropy spectrum (RAS) is observed from a Au(110) surface in a wide range of electrolytes and combinations of pH and applied potentials. It is suggested that this common RAS profile arises from an interaction between the potential applied to the Au(110) electrode and the dipole moments of oxidized species that locates the Fermi level at a common position with respect to the electronic band structure of Au. Rapid changes in this RAS profile are observed for Au(110)/H2SO4 as the potential is switched between 0.3 V and 0.6 V, a potential range in which the surface is not reconstructed and below the potential range of surface oxidation. The spectral changes are completed in less than 10 ms, are reversible and are attributed to the replacement of adsorbed anions by an oxygenated species.

Ledipasvir-Sofosbuvir for Treating Chronic Hepatitis C: A NICE Single Technology Appraisal-An Evidence Review Group Perspective

The National Institute for Health and Care Excellence (NICE) invited Gilead, the company manufacturing ledipasvir-sofosbuvir (LDV/SOF), to submit evidence for the clinical effectiveness and cost effectiveness of LDV/SOF for treating chronic hepatitis C. The School of Health and Related Research (ScHARR) Technology Assessment Group was commissioned as the Evidence Review Group (ERG). This paper describes the company's submission (CS), the ERG review and the subsequent decision of the NICE Appraisal Committee (AC). The ERG produced a critical review of the clinical effectiveness and cost-effectiveness evidence of LDV/SOF based upon the CS. The clinical effectiveness data for LDV/SOF were taken from ten trials: three phase III trials and seven phase II trials. Trials compared different durations of LDV/SOF, with and without ribavirin (RBV). There were no head-to-head trials comparing LDV/SOF with any comparator listed in the NICE scope. Data from the trials were mostly from populations with genotype 1 (GT1) disease, although some limited data were available for populations with genotypes 3 and 4. For GT1 treatment-naïve patients, sustained viral response for 12 weeks (SVR12) rates for LDV/SOF ranged from 93.1 to 99.4 % for subgroups of patients with non-cirrhotic disease, whilst SVR rates of 94.1 to 100 % were reported for subgroups of patients with compensated cirrhosis. For GT1 treatment-experienced patients, SVR12 rates ranging from 95.4 to 100 % were reported for subgroups of non-cirrhotic patients, and SVR rates ranging from 81.8 to 100 % were reported within subgroups of patients with compensated cirrhosis. Comparator data were not searched systematically as part of the submission, but were based on the company's previous NICE submission of sofosbuvir, with additional targeted searches. The ERG's critical appraisal of the company's economic evaluation highlighted a number of concerns. The ERG's base case analyses suggested that the incremental cost-effectiveness ratios (ICERs) for LDV/SOF (+RBV) are dependent on (a) treatment durations, (b) whether patients have been previously treated and (c) whether patients have liver cirrhosis or not. The AC concluded that it was appropriate to use the approach taken in the ERG's exploratory analyses, in line with the marketing authorisation, which considered people with and without cirrhosis separately, and estimated the cost effectiveness for each recommended treatment duration of LDV/SOF.

Inflammatory Response Influences Treatment of Localized Aggressive Periodontitis

We previously reported a systemic hyperinflammatory response to bacterial lipopolysaccharide (LPS) in children with localized aggressive periodontitis (LAP). Additionally, different levels of this response were observed within the LAP group. It is unknown whether this hyperinflammatory response influences the clinical response to periodontal treatment in these children. Therefore, the goal of this study was to evaluate the influence of LPS responsiveness present prior to treatment on the clinical response to treatment within the LAP cohort. Prior to treatment, peripheral blood was collected from 60 African American participants aged 5 to 21 y, free of systemic diseases, and diagnosed with LAP. Blood was stimulated with ultrapure LPS from Escherichia coli, and Luminex assays were performed to quantify 14 cytokine/chemokine levels. Principal component and cluster analyses were used to find patterns of cytokine/chemokine expression among participants and subdivide them into clusters. Three distinct clusters emerged among LAP participants: a high responder group (high level of response for INFg, IL6, and IL12p40), a mixed responder group (low for some and high for other cytokines/chemokines), and a low responder group (low overall cytokine/chemokine response). Periodontal clinical parameters were compared among these groups prior to and 3, 6, and 12 mo following treatment with mechanical debridement and systemic antibiotics. High responders presented the lowest reductions in clinical parameters after treatment, whereas the low responders presented the highest reductions. In our LAP participants, distinct patterns of LPS response were significantly predictive of changes in clinical parameters after treatment. Future studies are needed to evaluate the underlying mechanisms predicting the heterogeneity of LAP activity, severity, and response to treatment (ClinicalTrials.gov NCT01330719).

Randomized controlled trial comparing impact on platelet reactivity of twice-daily with once-daily aspirin in people with Type 2 diabetes

AIMS

Reduced aspirin efficacy has been demonstrated in people with Type 2 diabetes. Because increased platelet reactivity and/or turnover are postulated mechanisms, we examined whether higher and/or more frequent aspirin dosing might reduce platelet reactivity more effectively.

METHODS

Participants with Type 2 diabetes (n = 24) but without known cardiovascular disease were randomized in a three-way crossover design to 2-week treatment periods with aspirin 100 mg once daily, 200 mg once daily or 100 mg twice daily. The primary outcome was platelet reactivity, assessed using the VerifyNow(™) ASA method. Relationships between platelet reactivity and aspirin dosing were examined using generalized linear mixed models with random subject effects.

RESULTS

Platelet reactivity decreased from baseline with all doses of aspirin. Modelled platelet reactivity was more effectively reduced with aspirin 100 mg twice daily vs. 100 mg once daily, but not vs. 200 mg once daily. Aspirin 200 mg once daily did not differ from 100 mg once daily. Aspirin 100 mg twice daily was also more effective than once daily as measured by collagen/epinephrine-stimulated platelet aggregation and urinary thromboxane levels, with a similar trend measured by serum thromboxane levels. No episodes of bleeding occurred.

CONCLUSIONS

In Type 2 diabetes, aspirin 100 mg twice daily reduced platelet reactivity more effectively than 100 mg once daily, and numerically more than 200 mg once daily. Clinical outcome trials evaluating primary cardiovascular disease prevention with aspirin in Type 2 diabetes may need to consider using a more frequent dosing schedule.

The stability of the Au(1 1 0)-(1 × 3) surface reconstruction in electrochemical environments

Changes in the reflection anisotropy (RAS) profile of the Au(1 1 0)-(1  ×  3)/Na2SO4 interface over 25 h are attributed to the slow accumulation of impurities on the Au(1 1 0) surface which reduce the intensity of a transition involving a surface state that makes a positive contribution to the RAS profile at 1.8 eV. The growth in the intensity of a feature that makes a negative contribution to the RAS profile at 2.6 eV and the reduction in the intensity of contributions to higher energy is attributed to shifts in the energy of the surface band structure relative to the Fermi level caused by the accumulation of impurities. There is no clear explanation of the subsequent decay of the 2.6 eV feature or the long term reduction in intensity to high energy of the RAS profile.

The reflection anisotropy spectroscopy of the Au(1 1 0) surface structures in liquid environments

The reflection anisotropy (RAS) profiles of the Au(1 1 0)-(1  ×  1), (1  ×  2) and (1  ×  3) surface structures in electrochemical environments are shown to arise mainly from surface dipole transitions directed along the principal axes of the Au(1 1 0) surface. There are weak contributions to the RAS profiles of the Au(1 1 0)-(1  ×  1) and (1  ×  3) surfaces in the region of 4.0 eV which probably arise from (1 1 1) facets that are either intrinsic to the surface structures or are associated with steps. A transition involving a surface state just above the Fermi level, E F, contributes to the RAS profiles of the (1  ×  2) and (1  ×  3) surfaces but not to the RAS profile of the (1  ×  1) surface. A strong feature at 2.5 eV in the RAS profiles of the Au(1 1 0)-(1  ×  1) and (1  ×  2) surfaces is attributed to a transition in the vicinity of the L point of the Brillouin zone between the 5d band and the [Formula: see text] band at E F. It is argued that the applied potential of  -0.6 V, which creates the Au(1 1 0)-(1  ×  3) surface, lifts E F above the [Formula: see text] band causing it to become occupied and quenching this contribution to the RAS profile.

Diagnosis of suspected inherited platelet function disorders: results of a worldwide survey

BACKGROUND

Diagnosis of inherited platelet function disorders (IPFDs) is important for appropriate management and to improve epidemiologic and clinical knowledge. However, there remains a lack of consensus on the diagnostic approach.

OBJECTIVES

To gain knowledge on the current practices for the diagnosis of IPFD worldwide.

METHODS

A 67-item questionnaire was distributed to the ISTH members and to the members of several national hemostasis and thrombosis societies.

RESULTS

A total of 202 laboratories from 37 countries participated in the survey. The most frequent criterion to define patients with a suspected IPFD was a history of mucocutaneous bleeding and no acquired cause, but heterogeneity on the identification criteria was evident. Only 64.5% of respondents performed a direct clinical interview. On average, each laboratory studied 72 patients per year. The most commonly used laboratory equipment were the light-transmission aggregometer, the Platelet Function Analyzer-100, and the flow cytometer. Screening tests were platelet count, peripheral blood smear, light-transmission aggregometry, and Platelet Function Analyzer-100. Second-step tests were flow cytometry, molecular genetic analysis, and electron microscopy. Methodologies varied widely. In total, ~ 14,000 patients were investigated yearly and 60% turned out to not have a defect. Of the remaining 40%, only 8.7% received a diagnosis at a molecular level.

CONCLUSIONS

Many laboratories worldwide are involved in the diagnosis of IPFD. A large fraction of the patients studied remain without a diagnosis. A high variability in the diagnostic approaches is evident.

Conformational change in cytochrome P450 reductase adsorbed at a Au(110)-phosphate buffer interface induced by interaction with nicotinamide adenine dinucleotide phosphate

Changes observed in the reflection anisotropy spectroscopy (RAS) profiles of monolayers of cytochrome P450 reductase adsorbed at Au(110)-electrolyte interfaces at 0.056 V following the addition of nicotinamide adenine dinucleotide phosphate (NADP(+)) are explained in terms of a simple model as arising from changes in the orientation of an isoalloxazine ring located in the flavin mononucleotide binding domain of the protein. The model also accounts for the changes observed in the RAS as the potential applied to the Au(110) surface is varied and suggests that differences in the dependence of the RAS profile of the adsorbed protein on the potential applied to the electrode in the absence and presence of NADP(+) are explicable as arising from a competition between the applied potential acting to reduce the protein and the NADP(+) to oxidize it.

Particle size distribution of exosomes and microvesicles determined by transmission electron microscopy, flow cytometry, nanoparticle tracking analysis, and resistive pulse sensing

BACKGROUND

Enumeration of extracellular vesicles has clinical potential as a biomarker for disease. In biological samples, the smallest and largest vesicles typically differ 25-fold in size, 300,000-fold in concentration, 20,000-fold in volume, and 10,000,000-fold in scattered light. Because of this heterogeneity, the currently employed techniques detect concentrations ranging from 10(4) to 10(12) vesicles mL(-1) .

OBJECTIVES

To investigate whether the large variation in the detected concentration of vesicles is caused by the minimum detectable vesicle size of five widely used techniques.

METHODS

The size and concentration of vesicles and reference beads were measured with transmission electron microscopy (TEM), a conventional flow cytometer, a flow cytometer dedicated to detecting submicrometer particles, nanoparticle tracking analysis (NTA), and resistive pulse sensing (RPS).

RESULTS

Each technique gave a different size distribution and a different concentration for the same vesicle sample.

CONCLUSION

Differences between the detected vesicle concentrations are primarily caused by differences between the minimum detectable vesicle sizes. The minimum detectable vesicle sizes were 70-90 nm for NTA, 70-100 nm for RPS, 150-190 nm for dedicated flow cytometry, and 270-600 nm for conventional flow cytometry. TEM could detect the smallest vesicles present, albeit after adhesion on a surface. Dedicated flow cytometry was most accurate in determining the size of reference beads, but is expected to be less accurate on vesicles, owing to heterogeneity of the refractive index of vesicles. Nevertheless, dedicated flow cytometry is relatively fast and allows multiplex fluorescence detection, making it most applicable to clinical research.

Protein engineering and preclinical development of a GM-CSF receptor antibody for the treatment of rheumatoid arthritis

BACKGROUND AND PURPOSE

For antibody therapies against receptor targets, in vivo outcomes can be difficult to predict because of target-mediated clearance or antigen 'sink' effects. The purpose of this work was to engineer an antibody to the GM-CSF receptor α (GM-CSFRα) with pharmacological properties optimized for chronic, s.c. treatment of rheumatoid arthritis (RA) patients.

EXPERIMENTAL APPROACH

We used an in silico model of receptor occupancy to guide the target affinity and a combinatorial phage display approach for affinity maturation. Mechanism of action and internalization assays were performed on the optimized antibody in vitro before refining the modelling predictions of the eventual dosing in man. Finally, in vivo pharmacology studies in cynomolgus monkeys were carried out to inform the predictions and support future clinical development.

KEY RESULTS

Antibody potency was improved 8600-fold, and the target affinity was reached. The refined model predicted pharmacodynamic effects at doses as low as 1 mg kg(-1) and a study in cynomolgus monkeys confirmed in vivo efficacy at 1 mg kg(-1) dosing.

CONCLUSIONS AND IMPLICATIONS

This rational approach to antibody drug discovery enabled the isolation of a potent molecule compatible with chronic, s.c. self-administration by RA patients. We believe this general approach enables the development of optimal biopharmaceuticals.

Conformational change induced by electron transfer in a monolayer of cytochrome P450 reductase adsorbed at the Au(110)-phosphate buffer interface

The reflection anisotropy spectroscopy profiles of a variant of cytochrome P450 reductase adsorbed at the Au(110)-phosphate buffer interface depend on the sequence of potentials applied to the Au(110) electrode. It is suggested that this dependence arises from changes in the orientation of the isoalloxazine ring structures in the protein with respect to the Au(110) surface. This offers a method of monitoring conformational change in this protein by measuring variations in the reflection anisotropy spectrum arising from changes in the redox potential.