Recombinant C1 inhibitor in the prevention of severe COVID-19: a randomized, open-label, multi-center phase IIa trial.

Background: Conestat alfa (ConA), a recombinant human C1 inhibitor, may prevent thromboinflammation. Methods: We conducted a randomized, open-label, multi-national clinical trial in which hospitalized adults at risk for progression to severe COVID-19 were assigned in a 2:1 ratio to receive either 3 days of ConA plus standard of care (SOC) or SOC alone. Primary and secondary endpoints were day 7 disease severity on the WHO Ordinal Scale, time to clinical improvement within 14 days, and safety, respectively. Results: The trial was prematurely terminated because of futility after randomization of 84 patients, 56 in the ConA and 28 in the control arm. At baseline, higher WHO Ordinal Scale scores were more frequently observed in the ConA than in the control arm. On day 7, no relevant differences in the primary outcome were noted between the two arms (p = 0.11). The median time to defervescence was 3 days, and the median time to clinical improvement was 7 days in both arms (p = 0.22 and 0.56, respectively). Activation of plasma cascades and endothelial cells over time was similar in both groups. The incidence of adverse events (AEs) was higher in the intervention arm (any AE, 30% with ConA vs. 19% with SOC alone; serious AE, 27% vs. 15%; death, 11% vs. 0%). None of these were judged as being related to the study drug. Conclusion: The study results do not support the use of ConA to prevent COVID-19 progression. Clinical trial registration: https://clinicaltrials.gov, identifier NCT04414631.

Functional Activity of the Complement System in Hospitalized COVID-19 Patients: A Prospective Cohort Study.

AIMS: Although the exact factors promoting disease progression in COVID-19 are not fully elucidated, unregulated activation of the complement system (CS) seems to play a crucial role in the pathogenesis of acute lung injury (ALI) induced by SARS-CoV-2. In particular, the lectin pathway (LP) has been implicated in previous autopsy studies. The primary purpose of our study is to investigate the role of the CS in hospitalized COVID-19 patients with varying degrees of disease severity. METHODS: In a single-center prospective observational study, 154 hospitalized patients with PCR-confirmed SARS-CoV-2 infection were included. Serum samples on admission to the COVID-19 ward were collected for analysis of CS pathway activities and concentrations of LP proteins [mannose-binding lectin (MBL) and ficolin-3 (FCN-3)] & C1 esterase inhibitor (C1IHN). The primary outcome was mechanical ventilation or in-hospital death. RESULTS: The patients were predominately male and had multiple comorbidities. ICU admission was required in 16% of the patients and death (3%) or mechanical ventilation occurred in 23 patients (15%). There was no significant difference in LP activity, MBL and FCN-3 concentrations according to different peak disease severities. The median alternative pathway (AP) activity was significantly lower (65%, IQR 50-94) in patients with death/invasive ventilation compared to patients without (87%, IQR 68-102, p=0.026). An optimal threshold of <65.5% for AP activity was derived from a ROC curve resulting in increased odds for death or mechanical ventilation (OR 4,93; 95% CI 1.70-14.33, p=0.003) even after adjustment for confounding factors. Classical pathway (CP) activity was slightly lower in patients with more severe disease (median 101% for death/mechanical ventilation vs 109%, p=0.014). C1INH concentration correlated positively with length of stay, inflammatory markers and disease severity on admission but not during follow-up. CONCLUSION: Our results point to an overactivated AP in critically ill COVID-19 patients in vivo leading to complement consumption and consequently to a significantly reduced AP activity in vitro. The LP does not seem to play a role in the progression to severe COVID-19. Apart from its acute phase reaction the significance of C1INH in COVID-19 requires further studies.

The impact of the COVID-19 pandemic on autoimmune diagnostics in Europe: A lesson to be learned.

INTRODUCTION: The first wave of COVID-19 pandemic has disrupted almost all areas of the health care services to some extent throughout the world. Although the negative impact of COVID-19 on patients with autoimmune diseases has also been recognized, available data in this regard are limited. In the current study of the European Autoimmunity Standardisation Initiative (EASI) we aimed to provide reliable data on the extent of the impact of COVID-19 pandemic on test requests for different autoantibodies in European countries. METHODS: Data on test numbers and on the number of positive results were collected in 97 clinical laboratories from 15 European countries on a monthly basis for the year before (2019) and the year during (2020) the COVID-19 pandemic. RESULTS: A reduction in the number of autoantibody tests was observed in all European countries in the year 2020 compared to 2019. The reduction affected all autoantibody tests with an overall decrease of 13%, ranging from 1.4% (Switzerland) to 25.5% (Greece). In all countries, the decrease was most pronounced during the first wave of the pandemic (March-May 2020) with an overall decrease in those three months of 45.2%. The most affected autoantibodies were those commonly requested by general practitioners (anti-tTG IgA (-71%), RF IgM (-66%) and ACPA (-61%)). In the second wave of the pandemic (October-December 2020) the decrease was less pronounced (6.8%). With respect to the rate of positive results, subtle differences were observed for distinct autoantibodies during the pandemic, but the total rate of positive results was similar in both years. CONCLUSIONS: Our study demonstrated a strong decrease in autoantibody requests during the first wave of the COVID-19 pandemic in 15 European countries. The second wave was characterized by a less pronounced impact, with some participating countries hardly affected, while some other countries experienced a second decline. The decrease was clearly associated with the level of lock-down and with the required adjustments in the health care systems in different countries, supporting the importance of an effective strategy for the coordination of autoimmune testing in challenging situations as the COVID-19 pandemic.

Recombinant human C1 esterase inhibitor (conestat alfa) in the prevention of severe SARS-CoV-2 infection in hospitalized patients with COVID-19: A structured summary of a study protocol for a randomized, parallel-group, open-label, multi-center pilot trial (PROTECT-COVID-19).

OBJECTIVES: Conestat alfa, a recombinant human C1 esterase inhibitor, is a multi-target inhibitor of inflammatory cascades including the complement, the kinin-kallikrein and the contact activation system. The study objective is to investigate the efficacy and safety of conestat alfa in improving disease severity and short-term outcome in COVID-19 patients with pulmonary disease. TRIAL DESIGN: This study is an investigator-initiated, randomized (2:1 ratio), open-label, parallel-group, controlled, multi-center, phase 2a clinical trial. PARTICIPANTS: This trial is conducted in 3 hospitals in Switzerland, 1 hospital in Brazil and 1 hospital in Mexico (academic and non-academic). All patients with confirmed SARS-CoV-2 infection requiring hospitalization for at least 3 calendar days for severe COVID-19 will be screened for study eligibility. INCLUSION CRITERIA: - Signed informed consent - Age 18-85 years - Evidence of pulmonary involvement on CT scan or X-ray of the chest - Duration of symptoms associated with COVID-19 ≤ 10 days - At least one of the following risk factors for progression to mechanical ventilation on the day of enrolment: 1) Arterial hypertension 2) ≥ 50 years 3) Obesity (BMI ≥ 30 kg/m2) 4) History of cardiovascular disease 5) Chronic pulmonary disease 6) Chronic renal disease 7) C-reactive protein > 35mg/L 8) Oxygen saturation at rest of ≤ 94% when breathing ambient air Exclusion criteria: - Incapacity or inability to provide informed consent - Contraindications to the class of drugs under investigation (C1 esterase inhibitor) - Treatment with tocilizumab or another IL-6R or IL-6 inhibitor before enrolment - History or suspicion of allergy to rabbits - Pregnancy or breast feeding - Active or anticipated treatment with any other complement inhibitor - Liver cirrhosis (any Child-Pugh score) - Admission to an ICU on the day or anticipated within the next 24 hours of enrolment - Invasive or non-invasive ventilation - Participation in another study with any investigational drug within the 30 days prior to enrolment - Enrolment of the study investigators, their family members, employees and other closely related or dependent persons INTERVENTION AND COMPARATOR: Patients randomized to the experimental arm will receive conestat alfa in addition to standard of care (SOC). Conestat alfa (8400 U followed by 4200 U every 8 hours) will be administered as a slow intravenous injection (5-10 minutes) over a 72-hour period (i.e. 9 administrations in total). The first conestat alfa treatment will be administered on the day of enrolment. The control group will receive SOC only. SOC treatment will be administered according to local institutional guidelines, including supplemental oxygen, antibiotics, corticosteroids, remdesivir, and anticoagulation. MAIN OUTCOMES: The primary endpoint of this trial is disease severity on day 7 after enrolment assessed by an adapted WHO Ordinal Scale for Clinical Improvement (score 0 will be omitted and score 6 and 7 will be combined) from 1 (no limitation of activities) to 7 (death). Secondary outcomes include (i) the time to clinical improvement (time from randomization to an improvement of two points on the WHO ordinal scale or discharge from hospital) within 14 days after enrolment, (ii) the proportion of participants alive and not having required invasive or non-invasive ventilation at 14 days after enrolment and (iii) the proportion of subjects without an acute lung injury (defined by PaO2/FiO2 ratio of ≤300mmHg) within 14 days after enrolment. Exploratory outcomes include virological clearance, C1 esterase inhibitor pharmacokinetics and changes in routine laboratory parameters and inflammatory proteins. RANDOMISATION: Subjects will be randomised in a 2:1 ratio to treatment with conestat alfa in addition to SOC or SOC only. Randomization is performed via an interactive web response system (SecuTrial®). BLINDING (MASKING): In this open-label trial, participants, caregivers and outcome assessors are not blinded to group assignment. NUMBERS TO BE RANDOMISED (SAMPLE SIZE): We will randomise approximately 120 individuals (80 in the active treatment arm, 40 in the SOC group). Two interim analyses after 40 and 80 patients are planned according to the Pocock adjusted levels αp = 0.0221. The results of the interim analysis will allow adjustment of the sample size (Lehmacher, Wassmer, 1999). TRIAL STATUS: PROTECT-COVID-19 protocol version 3.0 (July 07 2020). Participant recruitment started on July 30 2020 in one center (Basel, Switzerland, first participant included on August 06 2020). In four of five study centers patients are actively recruited. Participation of the fifth study center (Mexico) is anticipated by mid December 2020. Completion of trial recruitment depends on the development of the SARS-CoV-2 pandemic. TRIAL REGISTRATION: Clinicaltrials.gov, number: NCT04414631 , registered on 4 June 2020 FULL PROTOCOL: The full protocol is attached as an additional file, accessible from the Trials website (Additional file 1). In the interest of expediting dissemination of this material, the familiar formatting has been eliminated; this Letter serves as a summary of the key elements of the full protocol.

Treatment of COVID-19 With Conestat Alfa, a Regulator of the Complement, Contact Activation and Kallikrein-Kinin System.

A dysregulated immune response with hyperinflammation is observed in patients with severe coronavirus disease 2019 (COVID-19). The aim of the present study was to assess the safety and potential benefits of human recombinant C1 esterase inhibitor (conestat alfa), a complement, contact activation and kallikrein-kinin system regulator, in severe COVID-19. Patients with evidence of progressive disease after 24 h including an oxygen saturation <93% at rest in ambient air were included at the University Hospital Basel, Switzerland in April 2020. Conestat alfa was administered by intravenous injections of 8400 IU followed by 3 additional doses of 4200 IU in 12-h intervals. Five patients (age range, 53-85 years; one woman) with severe COVID-19 pneumonia (11-39% lung involvement on computed tomography scan of the chest) were treated a median of 1 day (range 1-7 days) after admission. Treatment was well-tolerated. Immediate defervescence occurred, and inflammatory markers and oxygen supplementation decreased or stabilized in 4 patients (e.g., median C-reactive protein 203 (range 31-235) mg/L before vs. 32 (12-72) mg/L on day 5). Only one patient required mechanical ventilation. All patients recovered. C1INH concentrations were elevated before conestat alfa treatment. Levels of complement activation products declined after treatment. Viral loads in nasopharyngeal swabs declined in 4 patients. In this uncontrolled case series, targeting multiple inflammatory cascades by conestat alfa was safe and associated with clinical improvements in the majority of severe COVID-19 patients. Controlled clinical trials are needed to assess its safety and efficacy in preventing disease progression.

A Randomized Trial of Recombinant Human C1-Esterase-Inhibitor in the Prevention of Contrast-Induced Kidney Injury.

OBJECTIVES: This study sought to determine the efficacy profile and safety of recombinant human C1 esterase inhibitor (rhC1INH) in the prevention of contrast-associated acute kidney injury after elective coronary angiography. BACKGROUND: Contrast-associated acute kidney injury is caused by tubular cytotoxicity and ischemia/reperfusion injury. rhC1INH is effective in reducing renal ischemia/reperfusion injury in experimental models. METHODS: In this placebo-controlled, double-blind, single-center trial 77 patients with chronic kidney disease were randomized to receive 50 IU/kg rhC1INH before and 4 h after elective coronary angiography or placebo. The primary outcome was the peak change of urinary neutrophil gelatinase-associated lipocalin within 48 h, a surrogate marker of kidney injury. RESULTS: Median peak change of urinary neutrophil gelatinase-associated lipocalin was lower in the rhC1INH group (4.7 ng/ml vs. 22.5 ng/ml; p = 0.038) in the per-protocol population but not in the modified intention-to-treat analysis, and in patients with percutaneous coronary interventions (median, 1.8 ng/ml vs. 26.2 ng/ml; p = 0.039 corresponding to a median proportion peak change of 11% vs. 205%; p = 0.002). The incidence of a cystatin C increase ≥10% within 24 h was lower in the rhC1INH group (16% vs. 33%; p = 0.045), whereas the frequency of contrast-associated acute kidney injury was comparable. Adverse events during a 3-month follow-up were similarly distributed. CONCLUSIONS: Administration of rhC1INH before coronary angiography may attenuate renal injury as reflected by urinary neutrophil gelatinase-associated lipocalin and cystatin C. The safety profile of rhC1INH was favorable in a patient population with multiple comorbidities. (Recombinant Human C1 Esterase Inhibitor in the Prevention of Contrast-induced Nephropathy in High-risk Subjects [PROTECT]; NCT02869347).

Co-Occurrence of ANCA-Associated Vasculitis and Sjögren's Syndrome in a Patient With Acromegaly: A Case Report and Retrospective Single-Center Review of Acromegaly Patients.

Background: ANCA-associated vasculitis (AAV) and Sjögren's syndrome (SS) are uncommon autoimmune diseases. The co-occurrence in the same patient has been rarely described. Acromegaly has been associated with autoimmune thyroiditis, but the prevalence of other autoimmune disorders such as AAV and SS has not been evaluated in acromegaly. Methods: Characterization of a patient with acromegaly and two rare autoimmune diseases-SS and AAV (microscopic polyangiitis (MPA))-by autoantibody-array and whole exome sequencing (WES). Single-center retrospective review of medical records of acromegaly patients to explore the prevalence of diagnosed autoimmune diseases. Results: We report a Caucasian woman in her 50's with a serologically (anti-SSA/Ro, anti-MPO-ANCA antibodies) and histologically confirmed diagnosis of symptomatic SS and MPA. SS with MPO-ANCA positivity preceded MPA. An exploratory autoantigen array detected a broad spectrum of autoantibodies. WES revealed heterozygous carrier status of the PTPN22 mutation R620W, which is associated with an increased risk for autoimmunity. A similar combination of positive anti-SSA/Ro autoantibodies and ANCA was only present in 5/1184 (0.42%) other patients tested for both antibodies in our clinic over six years. Amongst 85 acromegaly patients seen at our clinic in a 20-year period, 12% had a clinically relevant associated immunological disease. Conclusion: We present a rare case of SS and AAV in a patient with acromegaly and multiple autoantibody specificities. Patients with SS and ANCA should be closely monitored for the development of (subclinical) AAV. Whether acromegaly represents a risk for autoimmunity should be further investigated in prospective acromegaly cohorts.

Role of lectin pathway complement proteins and genetic variants in organ damage and disease severity of systemic sclerosis: a cross-sectional study.

BACKGROUND: The role of the complement system in the pathogenesis of systemic sclerosis (SSc) is controversial. This study investigated the role of the lectin pathway of complement as a mediator of ischemia/reperfusion injury in SSc. METHODS: This is a prospective observational cross-sectional study of 211 SSc patients and 29 patients with Raynaud's phenomenon in undifferentiated connective tissue disease (UCTD) at risk of developing SSc from two outpatient clinics. Serum levels of lectin pathway proteins (FCN-2, FCN-3, MBL, and MASP-2) and eight MBL2 and FCN2 single-nucleotide polymorphisms (SNP) were analyzed by sandwich-type immunoassays and genotyping and examined for their association with disease manifestations. RESULTS: Lectin pathway protein levels and SNPs were similar between SSc and UCTD patients. FCN-2 levels were however higher in SSc patients with present evidence of digital ulcers (mean 1.4 vs. 1.0 µg/mL, p = 0.05), pitting scars (mean 1.3 vs. 1.0 µg/mL, p = 0.01), and puffy fingers (mean 1.2 vs. 1.0 µg/mL, p = 0.04). Similarly, higher FCN-2 levels were observed in SSc patients with Scl-70 autoantibodies (mean 1.5 vs. 1.0 µg/mL, p = 0.001), interstitial lung disease (mean 1.2 vs. 0.9 µg/mL, p = 0.02), and a forced vital capacity (FVC) below 80% (mean 1.4 vs. 1.0 µg/mL, p = 0.02). In line, variant alleles in the FCN-2 SNP at position + 6359 were associated with a significantly reduced FVC and diffusion capacity. Furthermore, patients with SSc renal crisis harbored higher MBL levels (mean 2.7 vs. 1.5 µg/mL, p = 0.04). No other lectin pathway protein levels or polymorphisms were associated with disease manifestations, low complement C3 and/or C4 levels, or inflammatory markers. CONCLUSIONS: This study does not support a relevant role for several lectin pathway complement proteins in the pathogenesis of SSc. Higher FCN-2 levels were however associated with Scl-70 autoantibody positivity, interstitial lung involvement, and digital vasculopathy. Elevated MBL levels were associated with renal crisis.

Delayed-type allergy to cobalt-comparison of a flow cytometric lymphocyte proliferation test with patch testing.

BACKGROUND: The patch test is the standard procedure for diagnosing delayed-type sensitization. If a patch test is not possible, the flow cytometric lymphocyte proliferation test (LPT), which determines the number and type of cells responding to a specific antigen in vitro, might be considered as an alternative. OBJECTIVES: Our aim was to establish a flow cytometric LPT for the detection of delayed-type allergic responses to cobalt, and to determine the correlation between stimulation indices (SIs) in LPT and the grade of patch test reactions. With the patch test as a diagnostic reference, we also assessed the sensitivity and specificity of the LPT. METHODS: Fifty-four patients patch tested with the baseline series including cobalt (CoCl2 ) were additionally tested with the flow cytometric LPT with CoCl2 . RESULTS: There was a significant correlation between the results of both tests: rs = 0.43; P = .001. The LPT with CoCl2 showed a sensitivity of 52.6% and a specificity of 85.7%. Corresponding to the low sensitivity of the LPT, high likelihood ratios for a positive patch test reaction were reached only in cases of strong lymphocyte proliferation (SI ≥ 10). CONCLUSIONS: In cases of clearly increased SIs, the flow cytometric LPT with CoCl2 gives relevant diagnostic information, and represents a valuable alternative to patch testing.

Rituximab Maintenance for a Maximum of 5 Years After Single-Agent Rituximab Induction in Follicular Lymphoma: Results of the Randomized Controlled Phase III Trial SAKK 35/03.

PURPOSE: Rituximab maintenance therapy has been shown to improve progression-free survival in patients with follicular lymphoma; however, the optimal duration of maintenance treatment remains unknown. PATIENTS AND METHODS: Two hundred seventy patients with untreated, relapsed, stable, or chemotherapy-resistant follicular lymphoma were treated with four doses of rituximab monotherapy in weekly intervals (375 mg/m(2)). Patients achieving at least a partial response were randomly assigned to receive maintenance therapy with one infusion of rituximab every 2 months, either on a short-term schedule (four administrations) or a long-term schedule (maximum of 5 years or until disease progression or unacceptable toxicity). The primary end point was event-free survival (EFS). Progression-free survival, overall survival (OS), and toxicity were secondary end points. Comparisons between the two arms were performed using the log-rank test for survival end points. RESULTS: One hundred sixty-five patients were randomly assigned to the short-term (n = 82) or long-term (n = 83) maintenance arms. Because of the low event rate, the final analysis was performed after 95 events had occurred, which was before the targeted event number of 99 had been reached. At a median follow-up period of 6.4 years, the median EFS was 3.4 years (95% CI, 2.1 to 5.3) in the short-term arm and 5.3 years (95% CI, 3.5 to not available) in the long-term arm (P = .14). Patients in the long-term arm experienced more adverse effects than did those in the short-term arm, with 76% v 50% of patients with at least one adverse event (P < .001), five versus one patient with grade 3 and 4 infections, and three versus zero patients discontinuing treatment because of unacceptable toxicity, respectively. There was no difference in OS between the two groups. CONCLUSION: Long-term rituximab maintenance therapy does not improve EFS, which was the primary end point of this trial, or OS, and was associated with increased toxicity.

Clinical significance of coexisting antitopoisomerase I and anticentromere antibodies in patients with systemic sclerosis: a EUSTAR group-based study.

OBJECTIVES: To determine the clinical characteristics of simultaneous occurrence of antitopoisomerase (ATA) and anticentromere (ACA) autoantibodies in systemic sclerosis (SSc). METHODS: Data of patients (n=4,687) fulfilling the ACR criteria for SSc and followed in the EULAR Scleroderma Trials and Research (EUSTAR) cohort were analysed. Sera from patients with simultaneous ATA and ACA were reanalyzed centrally by indirect immunofluorescence, enzyme immunoassay, and immunoblot to confirm antibody status. RESULTS: A total of 29 patients (0.6%) had been documented double-positive for both ATA and ACA in the EUSTAR database. Sera of 14 cases were available for central analysis, of which 8 were confirmed to unequivocally contain both antibodies. The double-positive patients were on average 52.4 years of age, 87.5% were female, and 62.5% had diffuse cutaneous (dc) SSc. Compared with matched ACA single-positive disease, cutaneous and visceral complications were more prevalent in double-positive cases, but this prevalence did not differ significantly in comparison to ATA single-positives. CONCLUSIONS: Coexistence of ATA and ACA can be found at low prevalence in SSc. The clinical features of double-positive patients are not clearly dissimilar to those of patients harbouring only ATA. The data do not support a direct involvement of these antibodies in the pathogenesis of established SSc, but may lack statistical power.

Synovial fluid metabolomics in different forms of arthritis assessed by nuclear magnetic resonance spectroscopy.

OBJECTIVES: Currently there are no reliable biomarkers in the synovial fluid available to differentiate between septic and non-septic arthritis or to predict the prognosis of osteoarthritis, respectively. Nuclear magnetic resonance (NMR) spectroscopy is an analytical technique that allows a rapid, high throughput metabolic profiling of biological fluids or tissues. METHODS: Proton (1H)-nuclear magnetic resonance (NMR) spectroscopy was performed in synovial fluid samples from patients with septic arthritis, crystal arthropathy, different forms of inflammatory arthritis or osteoarthritis (OA). The metabolic environment based on the low molecular weight components was compared in disease subsets and principal component analysis (PCA) was performed. RESULTS: Fifty-nine samples from patients with OA, gout, calcium pyrophosphate disease, spondylarthritis, septic arthritis and rheumatoid arthritis (RA) were analysed. NMR yielded stable and reproducible metabolites over time. Thirty-five different metabolites as well as paracetamol and ibuprofen were identified in synovial fluid. The metabolic profile of septic arthritis assessed by PCA was distinguishable from the other samples whereas no differences were seen in OA compared to crystal-associated arthritis, RA or spondylarthritis. CONCLUSIONS: 1H-NMR is a fast analytic tool with possible implications in synovial fluid diagnostics. A distinctive metabolism is observed in septic arthritis whereas metabolites in OA are similar to those in inflammatory arthritis.

[Abdominal pain, indigestion and eosinophilia]. / Troubles digestifs et hyperéosinophilie.

A 56 years old swiss man suffers of recurrent abdominal cramps with episodes of diarrhea and profuse expectorations. The routine laboratory shows principally a massive eosinophilia and elevated IgE in peripheral blood. After excluding the most frequent causes of eosinophilia, further laboratory investigations shows increased levels antinuclear and anti-SSA antibodies, elevated IgG4, increased pancreatic amylase and intestinal eosinophilia. We consider two etiologies: the hypereosinophilic syndrome, diagnostic of exclusion, and the autoimmune pancreatitis. Although we have not sufficient arguments in favour of an autoimmune pancreatitis, these two entities present some similar points.

Enumeration of antigen-specific CD8+ T lymphocytes by single-platform, HLA tetramer-based flow cytometry: a European multicenter evaluation.

BACKGROUND: HLA class I peptide tetramers represent powerful diagnostic tools for detection and monitoring of antigen-specific CD8(+) T cells. The impetus for the current multicenter study is the critical need to standardize tetramer flow cytometry if it is to be implemented as a routine diagnostic assay. Hence, the European Working Group on Clinical Cell Analysis set out to develop and evaluate a single-platform tetramer-based method that used cytomegalovirus (CMV) as the antigenic model. METHODS: Absolute numbers of CMV-specific CD8(+) T cells were obtained by combining the percentage of tetramer-binding cells with the absolute CD8(+) T-cell count. Six send-outs of stabilized blood from healthy individuals or CMV-carrying donors with CMV-specific CD8(+) T-cell counts of 3 to 10 cells/microl were distributed to 7 to 16 clinical sites. These sites were requested to enumerate CD8(+) T cells and, in the case of CMV-positive donors, CMV-specific subsets on three separate occasions using the standard method. RESULTS: Between-site coefficients of variation of less than 10% (absolute CD8(+) T-cell counts) and approximately 30% (percentage and absolute numbers of CMV-specific CD8(+) T cells) were achieved. Within-site coefficients of variation were approximately 5% (absolute CD8(+) T-cell counts), approximately 9% (percentage CMV-specific CD8(+) T cells), and approximately 17% (absolute CMV-specific CD8(+) T-cell counts). The degree of variation tended to correlate inversely with the proportion of CMV-specific CD8(+) T-cell subsets. CONCLUSIONS: The single-platform MHC tetramer-based method for antigen-specific CD8(+) T-cell counting has been evaluated by a European group of laboratories and can be considered a reproducible assay for routine enumeration of antigen-specific CD8(+) T cells.

A differentiated approach to assess the diagnostic usefulness of a rapid particle gel immunoassay for the detection of antibodies against heparin-platelet factor 4 in cardiac surgery patients.

Enzyme-linked immunosorbent assay (ELISA) methods have shown to be of a low specificity for confirming heparin-induced thrombocytopenia (HIT) in cardiac surgery patients. In other patient collectives, a new antigen test [ID-HPF4 Particle Gel Immuno Assay (PaGIA); Diamed, Cressier sur Morat, Switzerland] was recently reported to exhibit a better specificity than the ELISA. Since a more specific test would serve as a useful tool when diagnosing HIT, a prospective study was carried out to elucidate the specificity and diagnostic usefulness of PaGIA in cardiac surgical patients. As assessed in cardiac surgery patients without HIT, the proportion of PaGIA-positive samples was lowest at baseline (16%; 13/74), increasing to 31% (19/61) at postoperative days 5-9 (P = 0.06) and 69% (29/42) at postoperative days 10-18 (P < 0.001 versus postoperative days 5-9). The respective proportions in an ELISA (HPF4 ELISA; Stago, Asnières sur Seine, France) were lower. Because the prevalence of antibody positivity increases during the postoperative course, a differentiated mathematical model was used to assess predictive values and likelihood ratios (LR) of the PaGIA at three different phases of hospitalization. Calculating LR revealed -LR to be 0.07 at baseline, 0.09 during postoperative days 5-9, and 0.19 during postoperative days 10-18, while +LR were 5.9 at baseline, 3.0 during postoperative days 5-9, and 1.4 during postoperative days 10-18. Thus, in cardiac surgery patients, the PaGIA can be regarded as a useful tool in excluding rapid onset and typical onset of HIT, and further provides valuable information in the confirmation of rapid onset of HIT. Using a differentiated approach for calculation of predictive values and LR, the present study demonstrates that PaGIA, despite a lower specificity than the employed ELISA, in some situations is a valuable tool when diagnosing HIT in cardiac surgery patients.