Quantification of C1 inhibitor activity using a chromogenic automated assay: analytical and clinical performances.

OBJECTIVES: The quantification of functional C1 inhibitor activity (fC1-INH) is an important tool to diagnose bradykinin-mediated angioedema (AE), whether hereditary or acquired. For that an accurate assay is necessary, therefore we evaluated the analytical performances of a fC1-INH chromogenic assay (Berichrom®, Siemens) performed utilizing an Optilite turbidimeter (Binding Site). METHODS: fC1-INH was quantified by means of the chromogenic assay Berichrom®. Internal quality controls were used to determine the precision of the assay. Stability under various storage and matrix conditions, uncertainty, linearity, interference (of hemolysis, lipemia, and icterus), agreement with the manual Technochrom® assay, and diagnostic performances were further evaluated on samples from patients and healthy donors. RESULTS: The fC1-INH Berichrom® assay presented good performances regarding intra- and inter-assay precision (CV: 1.3-4.5 % and 3.0-6.0 %, respectively), expanded uncertainty (5.5 % at normal level and 12.5 % at the clinical threshold) and linearity (rho2>0.99: range 7-130 % activity). Addition of interfering substances (hemoglobin <16 g/L, intralipid® <12 g/L, and bilirubin <1 g/L) did not affect fC1-INH quantification. fC1-INH activity from healthy donors remained stable in citrate whole blood until 4 days at room temperature, and 7 days when plasma was collected. Agreement between the automated Berichrom® assay and the manual Technochrom® assay (n=47) was excellent as obtained with both quantitative (Deming regression and Bland-Altman difference plot) and qualitative (Kappa index=1) analyses. Finally, the diagnostic performance of the quantification of fC1-INH for AE evaluated on 81 patients revealed a sensitivity of 100 %, a specificity of 97.2 %, a positive predictive value of 83.3 % and a negative predictive value of 100 %. CONCLUSIONS: The automated fC1-INH Berichrom® assay showed good performance, both at the analytical and diagnostic/clinical levels that allowed its usage in a clinical laboratory for C1-INH-dependent bradykinin-mediated AE research in combination with quantitative C1-INH and C4 determinations.

Serum Human ß-Defensin 2 Is Increased in Angioedema Accompanying Chronic Spontaneous Urticaria.

INTRODUCTION: Chronic spontaneous urticaria (CSU) is a common cutaneous disease caused by mast-cell degranulation. Human ß-defensin 2 (HBD2) is a well-known antimicrobial peptide that is also a pruritogen inducing vascular permeability via non-IgE-mediated mast-cell degranulation. OBJECTIVE: We investigated the associations between serum HBD2 levels and the clinical characteristics of CSU patients. METHODS: Serum samples from 124 CSU patients and 56 healthy controls were screened for the levels of HBD2 and translationally controlled tumor protein (TCTP)_ by using ELISA. The urticaria activity score over 7 days (UAS7) was used to measure disease activity in CSU patients. Accompanying angioedema was self-reported. RESULTS: Serum HBD2 levels were higher in the CSU group than in healthy subjects (median [interquartile range], 84.1 [43.5, 142.5] vs. 59.5 [26.7, 121.5], p = 0.034). In CSU patients, serum HBD2 level was negatively correlated with the peripheral basophil percentages (Spearman's rho = -0.229, p = 0.01) and vitamin D levels (-0.262, p = 0.02), but positively correlated with TCTP levels (0.252, p = 0.006). In CSU patients, HBD2 level was higher in those with than without angioedema (101.7 [50.9, 184.2] vs. 66.7 [37.9, 132.0], p = 0.019). It did not differ by aspirin hypersensitivity or atopy status, or autologous serum skin test positivity. CONCLUSION: A known mast-cell degranulator, HBD2 was elevated in the sera from CSU patients compared to healthy controls and may be involved in the pathogenesis of accompanying angioedema.

Serum complexes between C1INH and C1INH autoantibodies for the diagnosis of acquired angioedema.

Acquired angioedema due to C1-inhibitor (C1INH) deficiency (AAE) is caused by secondary C1INH deficiency leading to bradykinin-mediated angioedema episodes. AAE typically presents in adulthood and is associated with B cell lymphoproliferation. Anti-C1INH autoantibodies (antiC1INHAbs) are detectable in a subset of AAE cases and considered a hallmark of the disease. When free antiC1INHAbs and malignant tumors are not detectable, diagnosis relies on the finding of low C1INH levels and/or function, lack of family history and SERPING1 mutations, age at onset and low or undetectable C1q levels, none of which is specific for AAE. We tested the diagnostic value of a novel enzyme-linked immunosorbent assay (ELISA) for the detection of circulating complexes between C1INH and antiC1INHAbs (C1INH-antiC1INHAb) in the serum of 20 European AAE patients characterized on the basis of their complement levels and function. Free antiC1INHAbs were detected in nine of 20 patients [six of immunoglobulin (Ig)G class, two of IgM class and one simultaneously presenting IgG and IgM classes], whereas C1INH-antiC1INHAb complexes were found in 18 of 20 of the AAE cases, regardless of the presence or absence of detectable free anti-C1INHAbs. Of note, nine of 20 patients showed negative free antiC1INHabs, but positive C1INH-antiC1INHAb complexes in their first measurement. In the cohort presented, IgM-class C1INH-antiC1INHAb are specifically and strongly associated with low C1q serum levels. Detection of C1INH-antiC1-INHAbs provides an added value for AAE diagnosis, especially in those cases in whom no free anti-C1INH antibodies are detected. The link between IgM-class C1INH-antiC1INHAb complexes and C1q consumption could have further implications for the development of autoimmune manifestations in AAE.

Pharmacogenetics of angiotensin-converting enzyme inhibitor-induced angioedema.

Angioedema is a rare adverse effect of the commonly used angiotensin-converting enzyme inhibitors (ACEi) and is reported to occur with a prevalence of 0.1%-0.7%. Although most ACEi-induced angioedema (ACEi-A) cases are mild, severe cases requiring intensive care and even resulting in death have been reported in the literature. The mechanisms underlying ACEi-A are not yet fully understood, but bradykinin and/or substance P accumulation resulting from inhibition of ACE is believed to play a crucial role. ACEi-A occurs at variable frequencies across different racial groups, suggesting a genetic association with the development of ACEi-A. To date, one genome-wide association study and several candidate gene studies have been published on the association of genetic variation with ACEi-A. Genetic associations reported have been attributed to several distinct mechanisms: (a) genes coding for alternative enzymes responsible for the degradation of bradykinin and/or substance P in the diminution of ACE activity (b) ACE gene function, (c) bradykinin receptor genes, (d) genes implicated in immune and inflammation regulation and (e) genes in the fibrinolytic and coagulation pathway. Despite several plausible genetic associations, there are currently no genetic variants with sufficient effect to be clinically useful. The low incidence of ACEi-A suggests that a combination of genomic approaches with the capability to detect potentially important variants might be required to shed light on the mechanism of this adverse reaction. Additionally, many non-genetic risk factors associated with ACEi-A suggest the potential contribution of epigenetic dysregulation.

Plasma kallikrein mediates brain hemorrhage and edema caused by tissue plasminogen activator therapy in mice after stroke.

Thrombolytic therapy using tissue plasminogen activator (tPA) in acute stroke is associated with increased risks of cerebral hemorrhagic transformation and angioedema. Although plasma kallikrein (PKal) has been implicated in contributing to both hematoma expansion and thrombosis in stroke, its role in the complications associated with the therapeutic use of tPA in stroke is not yet available. We investigated the effects of tPA on plasma prekallikrein (PPK) activation and the role of PKal on cerebral outcomes in a murine thrombotic stroke model treated with tPA. We show that tPA increases PKal activity in vitro in both murine and human plasma, via a factor XII (FXII)-dependent mechanism. Intravenous administration of tPA increased circulating PKal activity in mice. In mice with thrombotic occlusion of the middle cerebral artery, tPA administration increased brain hemorrhage transformation, infarct volume, and edema. These adverse effects of tPA were ameliorated in PPK (Klkb1)-deficient and FXII-deficient mice and in wild-type (WT) mice pretreated with a PKal inhibitor prior to tPA. tPA-induced brain hemisphere reperfusion after photothrombolic middle cerebral artery occlusion was increased in Klkb1-/- mice compared with WT mice. In addition, PKal inhibition reduced matrix metalloproteinase-9 activity in brain following stroke and tPA therapy. These data demonstrate that tPA activates PPK in plasma and PKal inhibition reduces cerebral complications associated with tPA-mediated thrombolysis in stroke.

Serum miR-125a-5p and CCL17 Upregulated in Chronic Spontaneous Urticaria and Correlated with Treatment Response.

Chronic spontaneous urticaria (CSU) is a common skin disorder associated with autoimmunity. MicroRNAs (miRNAs) are endogenous noncoding RNA molecules reported to be potential biomarkers for some autoimmune diseases. In this study, we investigated the association of miRNAs with CSU. A quantitative PCR (qPCR)-based array was generated from sera as obtained from 20 active CSU patients and 20 healthy controls. Upregulated or downregulated miRNAs were validated by reverse transcription qPCR in sera from 59 active CSU patients and 58 healthy controls. The expression of miR-125a-5p was significantly upregulated in CSU sera and serum levels of CCL17 were also significantly increased in CSU patients. Serum miR-125a-5p expressions were found to be further upregulated in refractory CSU cases (n = 10). In 12 CSU patients in remission, serum miR-125a-5p expression and CCL17 levels were significantly decreased as compared with that obtained in active phase patients. These results indicated that miR-125a-5p and CCL17 can serve as potential serum biomarkers for CSU.

Quantification of human C1 esterase inhibitor protein using an automated turbidimetric immunoassay.

BACKGROUND: Impaired levels or function of C1 inhibitor (C1-INH) results in angioedema due to increased bradykinin. It is important to distinguish between angioedema related to C1-INH deficiency and that caused by other mechanisms, as treatment options are different. In hereditary (HAE) and acquired (AAE) angioedema, C1-INH concentration is measured to aid patient diagnosis. Here, we describe an automated turbidimetric assay to measure C1-INH concentration on the Optilite® analyzer. METHODS: Linearity, precision, and interference were established over a range of C1-INH concentrations. The 95th percentile reference interval was generated from 120 healthy adult donors. To compare the Optilite C1-INH assay with a predicate assay used in a clinical laboratory, samples sent for C1-INH investigation were used. The predicate results were provided to allow comparison. RESULTS: The Optilite C1-INH assay was linear across the measuring range at the standard sample dilution. Intra and interassay variability was <6%. The 95th percentile adult reference interval for the assay was 0.21-0.38 g/L. There was a strong correlation between the Optilite concentrations and those generated with the predicate assay (R2  = 0.94, P < 0.0001, slope y = 0.83x). All patients with Type I HAE (n = 24) and AAE (n = 3) tested had concentrations below the measuring range in both assays, while all patients with unspecified angioedema (UAE), not diagnosed with HAE or AAE had values within the reference range. CONCLUSION: The Optilite assay allows the automated and precise quantification of C1-INH concentrations in patient samples. It could therefore be used as a tool to aid the investigation of patients with angioedema.

Potential Biomarkers for the Diagnosis of Angiotensin-Converting Enzyme Inhibitor-Induced Angioedema.

BACKGROUND: Angiotensin-converting enzyme inhibitor-induced angioedema (ACEi-AE) is the most frequent drug-induced angioedema. The aim of this study was to evaluate potential biomarkers for the detection of the risk to develop an ACEi-AE. METHODS: Adult patients who started antihypertensive treatment with ramipril were included and followed up for 4-6 weeks. At baseline, 3 days, and 4-6 weeks after onset of therapy, blood samples were obtained. RESULTS: Twenty-four patients could be enrolled. The thromboxane values were very heterogeneous, and none of the group differences observed was statistically significant. The values obtained for 6-keto-prostaglandin F1α (6-keto-PGF1α) showed a statistically significant increase with 10 mg/day doses under ramipril therapy. CONCLUSIONS: In this small patient population, it could be shown that determination of 6-keto-PGF1α is feasible. It may prove to be a valuable blood marker for assessing the risk of developing ACEi-AE.

Shortened Activated Partial Thromboplastin Time May Help in Diagnosing Hereditary and Acquired Angioedema.

OBJECTIVE: To evaluate whether activated partial thromboplastin time (APTT) could be used in the laboratory diagnosis of hereditary or acquired angioedema (HAE or AAE) with and without C1 inhibitor (C1-INH) deficiency. METHODS: In a prospective investigation, APTT and other coagulation parameters were determined in 149 adult patients with various types of angioedema and in 26 healthy participants (HP). RESULTS: Mean APTT was significantly shortened in HAE-C1-INH type I (p < 0.0001) and type II (p = 0.0017) and in AAE-C1-INH (p < 0.0001) compared to the HP. APTT was shortened under the reference range (26-36 s) in 33/45 (73.3%) patients with HAE-C1-INH, 10/15 (66.7%) patients with AAE-C1-INH, 4/27 (14.8%) patients with HAE with normal C1-INH, 1/32 (3.1%) patients with histaminergic angioedema, 4/30 (13.3%) patients with nonhistaminergic angioedema and in 2/26 (7.7%) HP. Thus, a shortened APTT was obtained in 8-9 times more patients with angioedema due to C1-INH deficiency when compared to patients with various forms of angioedema with normal C1-INH and also to HP. CONCLUSIONS: A shortened APTT may help to diagnose HAE-C1-INH and AAE-C1-INH when determination of C1-INH is not yet available.

Disease spectrum in patients with elevated serum tryptase levels.

BACKGROUND: Elevated serum tryptase levels can be a sign of mastocytosis, which is a rare disease associated with systemic and/or skin manifestations. OBJECTIVE: To investigate patients with elevated tryptase levels in regard to their underlying diseases, and to determine whether increased tryptase can be used as a diagnostic marker for underlying mastocytosis. METHODS: In a retrospective study the data of 96 patients with serum tryptase levels higher than 15 µg/L were systematically analysed. In 48 patients control investigations for baseline tryptase were performed. RESULTS: Fifty-three of the 96 patients had tryptase levels ≥20 µg/L. A mere 16% of the 96 patients suffered from mastocytosis and had the highest tryptase levels (P < 0.001). The remaining patients had anaphylaxis (36%), urticaria and angioedema (26%), local reactions to insect bites (4%), drug reactions (3%), or miscellaneous diagnoses (15%). Only 16 of these had acute symptoms at tryptase investigation. In all, 48 patients had a follow up; in 7/48 patients with acute symptoms normal tryptase levels were seen at control investigations, but 41/48 (85%) patients showed continuously elevated tryptase levels >15 µg/L and in 30 patients (62%) even values >20 µg/L; 11 of these patients had anaphylaxis, five urticaria, five other diagnoses and nine patients mastocytosis. CONCLUSION: More than 50% of patients with non-mastocytosis such as urticaria and angioedema, drug or anaphylactic reactions repeatedly had tryptase levels higher than 20 µg/L. Since baseline tryptase >20 µg/L is a minor criterion for mastocytosis, these patients should be inspected for skin lesions of mastocytosis and receive a diagnostic body work-up for systemic mastocytosis including a bone marrow biopsy.

[Biological investigation of kinin-mediated angioedema]. / Exploration biologique des angiœdèmes à kinines.

Kinin-mediated angioedema results from accumulation of kinins, vasoactive and vasopermeant peptides, on the vascular endothelium. The disease is characterized by sudden episodes of swelling in the subcutaneous and submucosal tissues; the edema may occur spontaneously or it may be precipitated by triggering factors such as physical or emotional stress, or certain medicines. The characterization of kinin formation and catabolism systems helps improve knowledge of the aetiopathogenic mechanisms involved and provides the basis for classification of kinin-mediated angioedema conditions; thus, we may distinguish between angioedema with C1 inhibitor deficiency, whether inherited or acquired, and angioedema with normal C1 inhibitor activity, associated with increased kinin-forming activity or deficiency in kinin catabolism enzymes. In support of the clinical diagnosis, the physician may request laboratory investigation for a functional and molecular definition of the disease. Laboratory diagnosis is based on the characterization of: (1) kinin production control by C1 inhibitor investigation (function, antigen levels and circulating species); (2) kinin production (kininogenase activity, kininogen cleavage species); and (3) kinin catabolism enzymes (aminopeptidase P, carboxypeptidase N, angiotensin-I converting enzyme and dipeptidyl peptidase IV). An abnormal biological phenotype is supported by examination of susceptibility genes (SERPING1, F12 and XPNPEP2) and mutation segregation in the families.

Clinical and laboratory characteristics that differentiate hereditary angioedema in 72 patients with angioedema.

BACKGROUND: Hereditary angioedema (HAE) is a rare but life-threatening condition that results from mutations in C1-inhibitor (C1-INH). Since distinguishing HAE from other causes of angioedema (AE) is a critical problem in emergencies, the objective of the present study was to clarify the differences between HAE and other forms of AE. METHODS: Seventy-two patients with AE were enrolled in this study. The medical history and laboratory data of patients with HAE at the first visit were compared to those with other types of AE. RESULTS: Subjects included 23 patients with HAE, 33 with mast cell-mediated AE, 5 with drug-induced AE and 11 with idiopathic AE. The average age of HAE onset (19.5 ± 8.0 years old) was significantly lower than in other groups. A family history of AE was noted in 82.6% of HAE patients, which was significantly higher than other groups. Swelling affecting the extremities and gastrointestinal (GI) tract was observed in the majority (60 to 80%) of HAE patients. Life threatening laryngeal edema was observed in 30.4% of HAE patients. In 95.6% of HAE patients serum levels of C4 were less than the lower limit of the normal range. In our subjects, the sensitivity and specificity of low C4 for HAE were 95.6% and 93.8%, respectively. CONCLUSIONS: Early onset of AE, positive family history, recurrent AE in the extremities and GI tract, and suffocation are distinctive characteristics of HAE. A low serum level of C4 is a useful marker for making a differential diagnosis of HAE.

Analysis of coagulation factors in angioedema/urticaria: increased values of D-dimer and fibrinogen in isolated angioedema.

INTRODUCTION: Recent research has shown that blood coagulation and the extrinsic coagulation cascade are involved in the pathogenesis of chronic spontaneous urticaria (CSU), but little is known about the coagulation factors in angioedema. METHODS: This study included 58 participants: 29 patients with chronic angioedema (14 with isolated angioedema and 15 with angioedema with wheals) and 29 healthy controls (HCs). We compared the values of coagulation factors in patients with isolated angioedema to those with wheals. Plasma levels of D-dimer, fibrinogen, and factor VII were measured by enzyme-linked immunosorbent assay (ELISA) for all participants. RESULTS: Significantly higher D-dimer (p = 0.016; ε² = 0.381) and fibrinogen (p = 0.044; ε² = 0.331) levels were recorded in patients with angioedema (both groups) than in the HCs, with higher levels for angioedema with wheals. Factor VII and fibrinogen levels did not differ significantly between the groups with angioedema, but coagulation factors were more often elevated in both angioedema groups than in HCs. CONCLUSIONS: One characteristic of angioedema is an elevated blood coagulation potential, which may help produce fibrin and may be important in controlling angioedema attacks.