Evaluation of cryoprotein investigation using a digital external quality assurance scheme

Background: Robust preanalytical and analytical processes are critical for the detection of cryoproteins. There is significant variation in practice in the detection, analysis and reporting. Results: A survey in 2018 of 137 laboratories participating in the UK National External Quality Assessment Service (UK NEQAS) (6) quality control program showed significant variation in the laboratory processes which highlighted the need for standardisation of the detection, analysis and reporting of cryoglobulins.Conclusion: The first available EQA scheme aiming to harmonise practice for cryoprotein testing has been developed by UK NEQAS and laboratories should participate in an appropriate EQA scheme to fulfil requirements for ISO accreditation.

A National Survey of Hereditary Angioedema and Acquired C1 Inhibitor Deficiency in the United Kingdom

BACKGROUND

Detailed demographic data on people with hereditary angioedema (HAE) and acquired C1 inhibitor deficiency in the United Kingdom are relatively limited. Better demographic data would be beneficial in planning service provision, identifying areas of improvement, and improving care.

OBJECTIVE

To obtain more accurate data on the demographics of HAE and acquired C1 inhibitor deficiency in the United Kingdom, including treatment modalities and services available to patients.

METHODS

A survey was distributed to all centers in the United Kingdom that look after patients with HAE and acquired C1 inhibitor deficiency to collect these data.

RESULTS

The survey identified 1152 patients with HAE-1/2 (58% female and 92% type 1), 22 patients with HAE with normal C1 inhibitor, and 91 patients with acquired C1 inhibitor deficiency. Data were provided by 37 centers across the United Kingdom. This gives a minimum prevalence of 1:59,000 for HAE-1/2 and 1:734,000 for acquired C1 inhibitor deficiency in the United Kingdom. A total of 45% of patients with HAE were on long-term prophylaxis (LTP) with the most used medication being danazol (55% of all patients on LTP). Eighty-two percent of patients with HAE had a home supply of acute treatment with C1 inhibitor or icatibant. A total of 45% of patients had a supply of icatibant and 56% had a supply of C1 inhibitor at home.

CONCLUSIONS

Data obtained from the survey provide useful information about the demographics and treatment modalities used in HAE and acquired C1 inhibitor deficiency in the United Kingdom. These data are useful for planning service provision and improving services for these patients.

Allergies and COVID-19 vaccines: An ENDA/EAACI Position paper

BACKGROUND

Anaphylaxis, which is rare, has been reported after COVID-19 vaccination, but its management is not standardized.

METHOD

Members of the European Network for Drug Allergy and the European Academy of Allergy and Clinical Immunology interested in drug allergy participated in an online questionnaire on pre-vaccination screening and management of allergic reactions to COVID-19 vaccines, and literature was analysed.

RESULTS

No death due to anaphylaxis to COVID-19 vaccines has been confirmed in scientific literature. Potential allergens, polyethylene glycol (PEG), polysorbate and tromethamine are excipients. The authors propose allergy evaluation of persons with the following histories: 1-anaphylaxis to injectable drug or vaccine containing PEG or derivatives; 2-anaphylaxis to oral/topical PEG containing products; 3-recurrent anaphylaxis of unknown cause; 4-suspected or confirmed allergy to any mRNA vaccine; and 5-confirmed allergy to PEG or derivatives. We recommend a prick-to-prick skin test with the left-over solution in the suspected vaccine vial to avoid waste. Prick test panel should include PEG 4000 or 3500, PEG 2000 and polysorbate 80. The value of in vitro test is arguable.

CONCLUSIONS

These recommendations will lead to a better knowledge of the management and mechanisms involved in anaphylaxis to COVID-19 vaccines and enable more people with history of allergy to be vaccinated.

Partial RAG deficiency in humans induces dysregulated peripheral lymphocyte development and humoral tolerance defect with accumulation of T-bet+ B cells

The recombination-activating genes (RAG) 1 and 2 are indispensable for diversifying the primary B cell receptor repertoire and pruning self-reactive clones via receptor editing in the bone marrow; however, the impact of RAG1/RAG2 on peripheral tolerance is unknown. Partial RAG deficiency (pRD) manifesting with late-onset immune dysregulation represents an ‘experiment of nature’ to explore this conundrum. By studying B cell development and subset-specific repertoires in pRD, we demonstrate that reduced RAG activity impinges on peripheral tolerance through the generation of a restricted primary B cell repertoire, persistent antigenic stimulation and an inflammatory milieu with elevated B cell-activating factor. This unique environment gradually provokes profound B cell dysregulation with widespread activation, remarkable extrafollicular maturation and persistence, expansion and somatic diversification of self-reactive clones. Through the model of pRD, we reveal a RAG-dependent ‘domino effect’ that impacts stringency of tolerance and B cell fate in the periphery.

Patients with partial recombination-activating gene (RAG) deficiency (pRD) present variable late-onset autoimmune clinical phenotypes. Walter and colleagues identified a restricted primary B cell antigen receptor repertoire enriched for autoreactivity and clonal persistence in pRD. They described dysregulated B cell maturation with expansion of T-bet⁺ B cells revealing how RAG impacts stringency of tolerance and B cell fate in the periphery.

The effect of infliximab dose escalation in inflammatory bowel disease patients with antibodies to infliximab

BACKGROUND

Infliximab dose escalation (DE) can be used in inflammatory bowel disease patient; however, the long-term benefit remains unclear, especially in those with antibodies to infliximab (ATI). The aim was to assess the effect of DE in patients with ATI on drug level, clinical response and ATI status.

METHODS

All patients undergoing infliximab DE (a reduction in dose interval between infusions <8 weeks ± an increase in dose up to 10 mg/kg) at a referral centre between April 2016 and August 2019 were included.

RESULTS

Ninety-two patients were DE: 51 were men, 50 had CD and 63 were receiving immunosuppression. A total of 87 people received DE for a median of 44 weeks (range 4-176). Five stopped infliximab after 1 dose of DE: 2 for loss of response and 3 for infusion reaction. In patients with ATI ≤10 vs. >10 AU/mL, DE significantly increased drug levels: median infliximab levels of 1.4 and 0.9 at baseline, respectively, to 3.2 and 3.5 at week 24. After DE, 21/35 ATI-positive patients had a fall in ATI ≤10 AU/mL. At week 24 following DE 62/92 patients were in clinical remission. Duration of clinical remission was shorter in those with ATI >10 AU/mL (median 24 weeks, range 0-88) than in those with transient/ATI ≤10 AU/mL (median 36 weeks, range 0-126, P = 0.06).

CONCLUSIONS

A strategy of DE for selected patients receiving infliximab is associated with an increase in drug levels and reduced ATI positivity. This is associated with clinical remission in approximately 70% of patients at 6 months.

Chronic urticaria in the real-life clinical practice setting in the UK: results from the noninterventional multicentre AWARE study

BACKGROUND

Chronic urticaria (CU) is a skin condition characterized by repeated occurrence of itchy weals and/or angio-oedema for > 6 weeks.

AIM

To provide data demonstrating the real-life burden of CU in the UK.

METHODS

This UK subset of the worldwide, prospective, noninterventional AWARE study included patients aged 18-75 years diagnosed with H1-antihistamine (H1-AH)-refractory chronic spontaneous urticaria (CSU) for > 2 months. Baseline characteristics, disease activity, treatments, comorbidities and healthcare resource use were documented. Quality of life (QoL), work productivity and activity impairment were assessed.

RESULTS

Baseline analysis included 252 UK patients. Mean age and body mass index were 45.0 years and 29.0 kg/m² , respectively. Most patients were female (77.8%) and had moderate/severe disease activity (mean Urticaria Activity Score over 7 days was 18.4) and a 'spontaneous' component to their CU (73.4% CSU; 24.6% CSU and chronic inducible urticaria). Common comorbidities included depression/anxiety (24.6%), asthma (23.8%) and allergic rhinitis (12.7%). A previous treatment was recorded for 57.9% of patients. Mean Dermatology Life Quality Index score was 9.5, and patients reported impairments in work productivity and activity. Healthcare resource use was high. Severity of CSU was associated with female sex, obesity, anxiety and diagnosis. Only 28.5% of patients completed all nine study visits, limiting analysis of long-term treatment patterns and disease impact.

CONCLUSIONS

Adult H1-AH-refractory patients with CU in the UK reported high rates of healthcare resource use and impairment in QoL, work productivity and activity at baseline. The differing structures of UK healthcare may explain the high study discontinuation rates versus other countries.

Loss of the interleukin-6 receptor causes immunodeficiency, atopy, and abnormal inflammatory responses

IL-6 excess is central to the pathogenesis of multiple inflammatory conditions and is targeted in clinical practice by immunotherapy that blocks the IL-6 receptor encoded by IL6R We describe two patients with homozygous mutations in IL6R who presented with recurrent infections, abnormal acute-phase responses, elevated IgE, eczema, and eosinophilia. This study identifies a novel primary immunodeficiency, clarifying the contribution of IL-6 to the phenotype of patients with mutations in IL6ST, STAT3, and ZNF341, genes encoding different components of the IL-6 signaling pathway, and alerts us to the potential toxicity of drugs targeting the IL-6R.

Bi-allelic Loss-of-Function CACNA1B Mutations in Progressive Epilepsy-Dyskinesia

The occurrence of non-epileptic hyperkinetic movements in the context of developmental epileptic encephalopathies is an increasingly recognized phenomenon. Identification of causative mutations provides an important insight into common pathogenic mechanisms that cause both seizures and abnormal motor control. We report bi-allelic loss-of-function CACNA1B variants in six children from three unrelated families whose affected members present with a complex and progressive neurological syndrome. All affected individuals presented with epileptic encephalopathy, severe neurodevelopmental delay (often with regression), and a hyperkinetic movement disorder. Additional neurological features included postnatal microcephaly and hypotonia. Five children died in childhood or adolescence (mean age of death: 9 years), mainly as a result of secondary respiratory complications. CACNA1B encodes the pore-forming subunit of the pre-synaptic neuronal voltage-gated calcium channel Ca_v2.2/N-type, crucial for SNARE-mediated neurotransmission, particularly in the early postnatal period. Bi-allelic loss-of-function variants in CACNA1B are predicted to cause disruption of Ca²⁺ influx, leading to impaired synaptic neurotransmission. The resultant effect on neuronal function is likely to be important in the development of involuntary movements and epilepsy. Overall, our findings provide further evidence for the key role of Ca_v2.2 in normal human neurodevelopment.

Flucloxacillin Hypersensitivity: Patient Outcomes in a Multicenter Retrospective Study

BACKGROUND

Flucloxacillin is a narrow-spectrum, beta-lactamase-resistant penicillin. Type I (IgE-mediated) and type IV (T-cell-mediated) reactions are less frequently reported than with other penicillins.

OBJECTIVE

To undertake a detailed clinical characterization of a cohort of patients referred with suspected flucloxacillin hypersensitivity.

METHODS

We retrospectively analyzed demographic characteristics, presentation, investigation, and management of 108 patients presenting to 4 UK centers. Patients underwent skin prick and intradermal testing with flucloxacillin, major (benzylpenicilloyl poly-l-lysine) and minor determinants, amoxicillin, and benzylpenicillin with immediate and, where appropriate, delayed reading of the test. In the immediate group, a further 14 patients were tested to ampicillin and 16 to Augmentin (co-amoxiclav-combination of clavulanic acid and amoxicillin). Skin test-negative patients underwent oral drug provocation. A multistep protocol was used, depending on risk assessment.

RESULTS

Forty of 108 (37%) patients were diagnosed with hypersensitivity to flucloxacillin, of whom 33 (82.5%) showed immediate and 7 (17.5%) nonimmediate hypersensitivity, respectively. In the immediate group, most reactions were severe: 19 of 33 (58%). Intradermal testing had a higher negative predictive value (86%) in the immediate group than in the nonimmediate group (67%). Only a minority of patients (6 of 17 [35%]) with IgE-mediated allergy were cross-sensitized on intradermal testing with other penicillins, compared with 3 of 4 (75%) in the delayed group.

CONCLUSIONS

Immediate hypersensitivity reactions to flucloxacillin are more common than delayed. Cross-sensitization to other penicillins appears higher in delayed reactions than in immediate. The negative predictive value of intradermal testing is higher in the immediate group than in the nonimmediate group. Drug provocation testing remains the diagnostic criterion standard.

Arthritis in Two Patients With Partial Recombination Activating Gene Deficiency

Autoimmunity is becoming an increasingly recognized complication in patients with primary immunodeficiencies (PIDs), including a variety of combined immune deficiencies such as Recombination Activating Gene (RAG) defects. The approach to treating autoimmunity in PID patients is complex, requiring a balance between immunosuppression and susceptibility to infection. Inflammatory arthritis is a feature of immune dysregulation in many PIDs, and the optimal treatment may differ from first line therapies that usually consist of disease-modifying anti rheumatic drugs (DMARDs). An example of mechanism-based therapy of arthritis in PID uses blockade of IL-6 signaling with tocilizumab for patients with STAT 3 gain-of-function (GOF) mutation and augmented IL-6 pathway. Herein, we describe two PID cases with arthritis who were found to have defects in RAG. One patient with refractory inflammatory arthritis experienced remarkable improvement in symptoms with tocilizumab therapy. Arthritis can be a clinical feature of immune dysregulation in RAG deficiency, and tocilizumab therapy has been suggested to have utility in treatment of arthritis in RAG deficiency.

Comprehensive Cancer-Predisposition Gene Testing in an Adult Multiple Primary Tumor Series Shows a Broad Range of Deleterious Variants and Atypical Tumor Phenotypes

Multiple primary tumors (MPTs) affect a substantial proportion of cancer survivors and can result from various causes, including inherited predisposition. Currently, germline genetic testing of MPT-affected individuals for variants in cancer-predisposition genes (CPGs) is mostly targeted by tumor type. We ascertained pre-assessed MPT individuals (with at least two primary tumors by age 60 years or at least three by 70 years) from genetics centers and performed whole-genome sequencing (WGS) on 460 individuals from 440 families. Despite previous negative genetic assessment and molecular investigations, pathogenic variants in moderate- and high-risk CPGs were detected in 67/440 (15.2%) probands. WGS detected variants that would not be (or were not) detected by targeted resequencing strategies, including low-frequency structural variants (6/440 [1.4%] probands). In most individuals with a germline variant assessed as pathogenic or likely pathogenic (P/LP), at least one of their tumor types was characteristic of variants in the relevant CPG. However, in 29 probands (42.2% of those with a P/LP variant), the tumor phenotype appeared discordant. The frequency of individuals with truncating or splice-site CPG variants and at least one discordant tumor type was significantly higher than in a control population (χ2 = 43.642; p ≤ 0.0001). 2/67 (3%) probands with P/LP variants had evidence of multiple inherited neoplasia allele syndrome (MINAS) with deleterious variants in two CPGs. Together with variant detection rates from a previous series of similarly ascertained MPT-affected individuals, the present results suggest that first-line comprehensive CPG analysis in an MPT cohort referred to clinical genetics services would detect a deleterious variant in about a third of individuals.

Unrestricted faecal calprotectin testing performs poorly in the diagnosis of inflammatory bowel disease in patients in primary care

Background

Faecal calprotectin (FC) measurement distinguishes patients with inflammatory bowel disease (IBD) from those with irritable bowel syndrome but evidence of its performance in primary care is limited.

Aims

To assess the yield of IBD from FC testing in primary care.

Methods

Retrospective review of hospital records to assess the outcome following FC testing in primary care. Investigations for all patients undergoing FC testing in a single laboratory for 6 months from 1 October 2013 to 28 February 2014 were reviewed.

Results

410 patients (162 male; median age 42; range 16–91) were included. FC>50 µg/g was considered positive (FC+). 148/410 (36.1%; median age 44 (17–91)) were FC+ (median FC 116.5 µg/g (51–1770)). 122/148 FC-positive patients (82.4%) underwent further investigation. 97 (65.5%) underwent lower gastrointestinal endoscopy (LGIE), of which 7 (7.2%) had IBD. 49/262 (18.7%) FC-negative (FC−) patients (FC ≤50 µg/g) (median age 47 (19–76)) also underwent LGIE, of whom 3 (6.1%) had IBD.

IBD was diagnosed in 11/410 (2.7%; 4 ulcerative colitis, 3 Crohn’s disease, 4 microscopic colitis). 8/11 were FC+ (range 67–1170) and 3 FC−. At a 50 µg/g threshold, sensitivity for detecting IBD was 72.7%, specificity 64.9%, positive predictive value (PPV) 5.41% and negative predictive value 98.9%. Increasing the threshold to 100 µg/g reduced the sensitivity of the test for detecting IBD to 54.6%.

Conclusions

FC testing in primary care has low sensitivity and specificity with poor PPV for diagnosing IBD. Its use needs to be directed to those with a higher pretest probability of disease. Local services and laboratories should advise general practitioners accordingly.

Multicentre, non-interventional study to assess the profile of patients with uncontrolled rhinitis prescribed a novel formulation of azelastine hydrochloride and fluticasone propionate in a single spray in routine clinical practice in the UK

OBJECTIVE

The aims of this study were (1) to characterise the type of patient prescribed MP-AzeFlu (Dymista, a novel formulation of azelastine hydrochloride, fluticasone propionate and excipients in a single spray) in real life in the UK and physicians' reasons for prescribing it and (2) to quantify the personal and societal burden of allergic rhinitis (AR) in the UK prior to MP-AzeFlu prescription.

DESIGN, SETTING AND PARTICIPANTS

This multicentre, non-interventional study enrolled patients (n=193) with moderate-to-severe AR and acute symptoms who were eligible to receive treatment with MP-AzeFlu according to its licensed indications. Information was gathered on patient demographics, AR history and symptom severity, symptomatology and AR treatments in the previous calendar year (prior to MP-AzeFlu prescription). Physicians also recorded the number of previous AR visits, specific reasons for these visits and their reason for prescribing MP-AzeFlu.

RESULTS

Most patients had seasonal AR either alone (10.4%) or in combination with perennial AR (35.2%), but many had AR of unknown origin (35.8%). Prior to MP-AzeFlu prescription, patients reported troublesome symptoms (78.2%) and sleep disturbance (64.8%), with congestion considered the most bothersome (54.4%) and ocular symptoms reported by 68.4% of patients. The most frequent reason for MP-AzeFlu prescription was that other therapies were not sufficient in the past (78.8%) or not sufficient to treat acute symptoms (16.1%). 79.3% of patients reported using ≥2 AR therapies in the past year. An average of 1.6 (SD 1.9) doctor visits due to AR were reported prior to MP-AzeFlu prescription.

CONCLUSIONS

In the UK, MP-AzeFlu was prescribed for individuals (≥12 years) with moderate/severe AR irrespective of (1) previous AR treatment (mono or multiple), (2) previous or likely treatment failure, (3) phenotype, (4) number of previous physician visits for AR and (5) for the relief of both acute symptoms and in anticipation of allergen exposure.

Chlorhexidine allergy in four specialist allergy centres in the United Kingdom, 2009-13: clinical features and diagnostic tests

We describe an observational survey of diagnostic pathways in 104 patients attending four specialist allergy clinics in the United Kingdom following perioperative hypersensitivity reactions to chlorhexidine reactions. The majority were life-threatening. Men undergoing urological or cardiothoracic surgery predominated. Skin prick testing and specific immunoglobulin (sIg)E testing were the most common tests used for diagnosis. Fifty-three per cent of diagnoses were made on the basis of a single positive test. Where multiple tests were performed the sensitivity of intradermal, basophil activation and skin prick testing was 68% (50-86%), 50% (10-90%) and 35% (17-55%), respectively. Seven per cent were negative on screening tests initially, and 12 cases were only positive for a single test despite multiple testing. Intradermal tests appeared most sensitive in this context. Additional sensitization to other substances used perioperatively, particularly neuromuscular blocking agents (NMBA), was found in 28 patients, emphasizing the need to test for possible allergy to all drugs to which the patient was exposed even where chlorhexidine is positive.

Drug allergy passport and other documentation for patients with drug hypersensitivity - An ENDA/EAACI Drug Allergy Interest Group Position Paper

The strongest and best-documented risk factor for drug hypersensitivity (DH) is the history of a previous reaction. Accidental exposures to drugs may lead to severe or even fatal reactions in sensitized patients. Preventable prescription errors are common. They are often due to inadequate medical history or poor risk assessment of recurrence of drug reaction. Proper documentation is essential information for the doctor to make sound therapeutic decision. The European Network on Drug Allergy and Drug Allergy Interest Group of the European Academy of Allergy and Clinical Immunology have formed a task force and developed a drug allergy passport as well as general guidelines of drug allergy documentation. A drug allergy passport, a drug allergy alert card, a certificate, and a discharge letter after medical evaluation are adequate means to document DH in a patient. They are to be handed to the patient who is advised to carry the documentation at all times especially when away from home. A drug allergy passport should at least contain information on the culprit drug(s) including international nonproprietary name, clinical manifestations including severity, diagnostic measures, potential cross-reactivity, alternative drugs to prescribe, and where more detailed information can be obtained from the issuer. It should be given to patients only after full allergy workup. In the future, electronic prescription systems with alert functions will become more common and should include the same information as in paper-based documentation.

The United Kingdom Primary Immune Deficiency (UKPID) Registry: report of the first 4 years' activity 2008-2012

This report summarizes the establishment of the first national online registry of primary immune deficency in the United Kingdom, the United Kingdom Primary Immunodeficiency (UKPID Registry). This UKPID Registry is based on the European Society for Immune Deficiency (ESID) registry platform, hosted on servers at the Royal Free site of University College, London. It is accessible to users through the website of the United Kingdom Primary Immunodeficiency Network (www.ukpin.org.uk). Twenty-seven centres in the United Kingdom are actively contributing data, with an additional nine centres completing their ethical and governance approvals to participate. This indicates that 36 of 38 (95%) of recognized centres in the United Kingdom have engaged with this project. To date, 2229 patients have been enrolled, with a notable increasing rate of recruitment in the past 12 months. Data are presented on the range of diagnoses recorded, estimated minimum disease prevalence, geographical distribution of patients across the United Kingdom, age at presentation, diagnostic delay, treatment modalities used and evidence of their monitoring and effectiveness.

BPIFB1 is a lung-specific autoantigen associated with interstitial lung disease

Interstitial lung disease (ILD) is a complex and heterogeneous disorder that is often associated with autoimmune syndromes. Despite the connection between ILD and autoimmunity, it remains unclear whether ILD can develop from an autoimmune response that specifically targets the lung parenchyma. We examined a severe form of autoimmune disease, autoimmune polyglandular syndrome type 1 (APS1), and established a strong link between an autoimmune response to the lung-specific protein BPIFB1 (bactericidal/permeability-increasing fold-containing B1) and clinical ILD. Screening of a large cohort of APS1 patients revealed autoantibodies to BPIFB1 in 9.6% of APS1 subjects overall and in 100% of APS1 subjects with ILD. Further investigation of ILD outside the APS1 disorder revealed BPIFB1 autoantibodies present in 14.6% of patients with connective tissue disease-associated ILD and in 12.0% of patients with idiopathic ILD. The animal model for APS1, Aire⁻/⁻ mice, harbors autoantibodies to a similar lung antigen (BPIFB9); these autoantibodies are a marker for ILD. We found that a defect in thymic tolerance was responsible for the production of BPIFB9 autoantibodies and the development of ILD. We also found that immunoreactivity targeting BPIFB1 independent of a defect in Aire also led to ILD, consistent with our discovery of BPIFB1 autoantibodies in non-APS1 patients. Overall, our results demonstrate that autoimmunity targeting the lung-specific antigen BPIFB1 may contribute to the pathogenesis of ILD in patients with APS1 and in subsets of patients with non-APS1 ILD, demonstrating the role of lung-specific autoimmunity in the genesis of ILD.

Defining the impact of individual sample variability on routine immunoassay of serum free light chains (sFLC) in multiple myeloma

Serum free light chain (sFLC) measurement has gained widespread acceptance and is incorporated into various diagnostic and response criteria. Non-linearity and antigen excess are the main causes of 'variability' in the measurement of sFLC using immunoassay, but the impact of these on measurement has been unclear. We performed a retrospective evaluation using a dilutional strategy to detect these phenomena. A total of 464 samples in 2009 and 373 samples in 2010 were analysed for sFLC. Non-linearity was detected in both high and apparently normal sFLC. Major non-linearity of more than twofold is common in high kappa (20·2%) and lambda (14·1%). It is less common in samples with apparently normal levels - kappa (6·4%) and lambda (9·5%). 9·4% of kappa and 15·5% of lambda showed antigen excess at screening dilutions. 34·4% of the samples had either non-linearity or antigen excess. We conclude that significant measurement variability is common in the measurement of sFLC. There is currently no reliable technique to detect non-linearity phenomena unless a serial dilution strategy is applied to every analysis. We recommend that laboratories routinely reporting sFLC results for clinical services need appropriate strategies for addressing these issues. Clinicians should be aware of these limitations in interpretation of sFLC assay for individual patients. Future guidelines should adopt action thresholds which are grounded firmly in test performance parameters.

Quality not quantity for transglutaminase antibody 2: the performance of an endomysial and tissue transglutaminase test in screening coeliac disease remains stable over time

National Institute of Clinical Excellence (NICE) and European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) guidance for the diagnosis of coeliac disease has been published. However, there is some controversy regarding the advice on the use of stratifying levels of immunoglobulin (IgA) tissue transglutaminase antibody (TG2) test positivity in the absence of test standardization and the vagueness of the indication to test equivocal samples. Using repeat service audit, we demonstrate that a combination of TG2 followed by IgA endomysial antibodies (EMA) is the best strategy for all degrees of mucosal abnormality using our test combination. Reliance upon immunoassay titre is not as effective, and cannot be applied consistently across populations in the absence of assay standardization. Guidelines advocating the use of tests should involve experts in laboratory diagnostics and external quality assurance to ensure that errors of generalization do not occur and that test performance is achievable in routine diagnostic use.

Raised tryptase without anaphylaxis or mastocytosis: heterophilic antibody interference in the serum tryptase assay

Mast cell tryptase (MCT) is a key diagnostic test for mastocytosis and anaphylaxis. High serum tryptase levels are also one of the risk factors for adverse reaction in venom immunotherapy, yet occasional patients are seen with raised levels in the absence of either diagnosis. False positive results can be due to assay interference by heterophilic antibodies such as rheumatoid factor (RF) and human anti-mouse antibodies (HAMA). We therefore investigated heterophilic antibody interference by rheumatoid factor activity and HAMA as a cause of raised MCT results in the Phadia tryptase assay. Serum samples from 83 patients were assayed for MCT and rheumatoid factor before and after the use of heterophilic antibody blocking tubes (HBT). Samples with more than 17% reduction in MCT with detectable RF were then assayed for HAMA. Fourteen (17%) of the 83 samples with positive RF showed a >17% decrease in mast cell tryptase after HBT blocking. Post-HBT, eight of 14 (57%) reverted from elevated to normal range values with falls of up to 98%. RF levels were also decreased significantly (up to 75%). Only one of the 83 tested was apparently affected by HAMA in the absence of detectable IgM RF. In conclusion, any suspicious MCT result should be checked for heterophilic antibodies to evaluate possible interference. False positive MCT levels can be caused by rheumatoid factor. We suggest a strategy for identifying assay interference, and show that it is essential to incorporate this caveat into guidance for interpretation of MCT results.

NOD2 polymorphisms in clinical phenotypes of common variable immunodeficiency disorders

Common variable immunodeficiency disorders (CVIDs) are a heterogeneous group of diseases characterized by hypogammaglobulinaemia and consequent susceptibility to infection. CVID patients commonly develop a variety of additional manifestations for which the causative factors are not fully understood. Two such manifestations are granulomatous disease and enteropathy. Because the ability to predict complications would aid clinical management, we continue to search for possible disease modifier genes. NOD2 acts a microbial sensor and is involved in proinflammatory signalling. Particular mutations of the NOD2 gene are associated with Crohn's disease including gly908arg, leu1007finsc and arg702trp polymorphisms. We hypothesized that NOD2 polymorphisms may be a disease modifier gene towards an enteropathic or granulomatous phenotype within CVIDs. Sequence-specific primers returned genotypes for 285 CVID patients from centres across the United Kingdom and Europe. We present the frequencies of the different phenotypes of patients within our international cohort. Arg702trp polymorphisms were significantly less frequent than wild-type (WT) (P = 0·038) among international CVID patients with splenomegaly. Gly908arg polymorphisms were more prevalent than WT in UK patients with autoimmune disorders (P = 0·049) or enteropathy (P = 0·049). NOD2 polymorphisms were not more prevalent than WT in CVID patients with clinical phenotypes of granulomata. UK allele frequencies of 0·014, 0·056 and 0·026 were found for gly908arg, arg702trp and leu1007finsc NOD2 polymorphisms, respectively. These do not differ significantly from UK immunocompetent controls confirming, as expected, that in addition these NOD2 polymorphisms do not confer susceptibility to CVIDs per se.

Cryoglobulin evaluation: best practice?

Cryoglobulins are serum immunoglobulins that precipitate at temperatures below 37 degrees C and re-dissolve on warming. Cryoglobulinaemia leads to variable symptoms including characteristic purpura, ischaemia of extremities, renal failure, peripheral neuropathy, abdominal pain secondary to intestinal ischaemia and arthralgias. Cryoglobulin testing is underutilized in clinical practice. It has been neglected in clinical laboratories and by clinicians due to several factors, such as the length of time it takes for serum cryoglobulin analysis to be performed in the laboratory, the perceived difficulty in getting optimal sampling conditions and a failure to appreciate that even apparently low levels of cryoglobulin can be associated with severe symptoms in some patients. The most important variable confounding standardization of cryoglobulin testing is improper sample handling. A recent report critically appraising the current practice of cryoglobulin evaluation in 137 laboratories in Europe by United Kingdom National External Quality Assurance Scheme (UKNEQAS) illustrated the wide variability in practice. Although many clinical laboratories perform cryoglobulin evaluation, there are widespread differences in the methodology used and the care with which this is carried out and this leads to considerable intralaboratory and interlaboratory variability. The most common sources of error are false-negative results due to loss of cryoprecipitate during transport and storage. Better standardization is needed to avoid missed diagnoses and improve the comparability of results. Laboratories should ensure that sample temperature is maintained at 37 degrees C until the serum is separated. In this article, we briefly review the classification and clinical features of cryoglobulins and suggest best practice guidelines for laboratory detection and identification of cryoglobulins.