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Davidson F.,Clinical Biochemistry | Lock R.J.,Immunology and Immunogenetics
Annals of Clinical Biochemistry | Year: 2017

Background: Faecal calprotectin has been shown to be a useful non-invasive marker for the diagnosis and monitoring of inflammatory bowel disease in children and adults. Although there are well-established reference ranges for the diagnosis of inflammatory bowel disease in adults, these have been less well studied in children. The objective was to establish reference ranges in our local population. Method: All faecal calprotectin results from 2011 to 2014 were retrospectively collated and grouped according to patient age. Probability plots were used to determine expected upper limit of normal for each age group, and Mann-Whitney test was used to determine statistical difference between groups. Results: Upper limit of normal for age groups 1–3.9 years, 4–17.9 years and 18 years plus were 77, 62 and 61 µg/g, respectively. There was a significant difference (P = 0.0013) between the median calprotectin concentration for the age group 1–3.9 years (n = 87) and 4–17.9 years (n = 636) and between the age group 1–3.9 years and 18 years plus (n = 7953, P = 0.0001), but there was no significant difference between the age groups 4–17.9 years and 18 years plus (P = 0.4206). Conclusions: In our local population, faecal calprotectin varies with age. Children aged 1–3.9 years had higher concentrations of faecal calprotectin than adults, but there was no significant difference in faecal calprotectin between older children and adults. This is in agreement with other published studies; however, the faecal calprotectin upper limit of normal calculated for children aged 1–3.9 years was lower than has been observed elsewhere. © 2016, © The Author(s) 2016.


Egner W.,Sheffield Teaching Hospitals NHS TrustUK NEQAS ImmunologySheffield | Lock R.J.,Immunology and Immunogenetics | Patel D.,Sheffield Teaching Hospitals NHS TrustUK NEQAS ImmunologySheffield
Clinical and Experimental Immunology | Year: 2016

Immunoglobulin (Ig)G4 disease can have apparently 'normal' levels of IgG4 due to antigen excess conditions. IgG4 measurement therefore appears falsely low. UK National External Quality Assurance Scheme (UK NEQAS) data and other reports have suggested that this problem occurred despite pre-existing antigen excess detection steps. To determine the clinical relevance of the problem, we examined the prevalence and characteristics of prozoning in our laboratory and patient cohorts. We establish that the prevalence of raised IgG4 in routine IgG4 analysis is low (< 1%) using one of the two routine methods in use in the United Kingdom. We show that subsequent assay modification appears to have reduced the likelihood of misleading readings. However, the original version of the assay prozoned to low levels (below 0·64 g/l) in 41% of high IgG4 samples in our patients. This may explain the previous reports of low sensitivity of raised IgG4 for IgG4RD, and predictive values should be re-evaluated in this disease using modified prozone-resistant protocols. All laboratories providing IgG4 measurements should verify that their assays are fit for the clinical quality requirement of detection raised IgG4 levels and must verify the upper limit of their reference ranges and freedom from prozoning. © 2016 British Society for Immunology.


Egner W.,Sheffield Teaching Hospitals NHS Trust | Lock R.J.,Immunology and Immunogenetics | Patel D.,Sheffield Teaching Hospitals NHS Trust
Clinical and Experimental Immunology | Year: 2016

Immunoglobulin (Ig)G4 disease can have apparently ‘normal’ levels of IgG4 due to antigen excess conditions. IgG4 measurement therefore appears falsely low. UK National External Quality Assurance Scheme (UK NEQAS) data and other reports have suggested that this problem occurred despite pre-existing antigen excess detection steps. To determine the clinical relevance of the problem, we examined the prevalence and characteristics of prozoning in our laboratory and patient cohorts. We establish that the prevalence of raised IgG4 in routine IgG4 analysis is low (< 1%) using one of the two routine methods in use in the United Kingdom. We show that subsequent assay modification appears to have reduced the likelihood of misleading readings. However, the original version of the assay prozoned to low levels (below 0·64 g/l) in 41% of high IgG4 samples in our patients. This may explain the previous reports of low sensitivity of raised IgG4 for IgG4RD, and predictive values should be re-evaluated in this disease using modified prozone-resistant protocols. All laboratories providing IgG4 measurements should verify that their assays are fit for the clinical quality requirement of detection raised IgG4 levels and must verify the upper limit of their reference ranges and freedom from prozoning. © 2016 British Society for Immunology


PubMed | Sheffield., Sheffield Teaching Hospitals NHS Trust and Immunology and Immunogenetics
Type: Journal Article | Journal: Clinical and experimental immunology | Year: 2016

Immunoglobulin (Ig)G4 disease can have apparently normal levels of IgG4 due to antigen excess conditions. IgG4 measurement therefore appears falsely low. UK National External Quality Assurance Scheme (UK NEQAS) data and other reports have suggested that this problem occurred despite pre-existing antigen excess detection steps. To determine the clinical relevance of the problem, we examined the prevalence and characteristics of prozoning in our laboratory and patient cohorts. We establish that the prevalence of raised IgG4 in routine IgG4 analysis is low (< 1%) using one of the two routine methods in use in the United Kingdom. We show that subsequent assay modification appears to have reduced the likelihood of misleading readings. However, the original version of the assay prozoned to low levels (below 064 g/l) in 41% of high IgG4 samples in our patients. This may explain the previous reports of low sensitivity of raised IgG4 for IgG4RD, and predictive values should be re-evaluated in this disease using modified prozone-resistant protocols. All laboratories providing IgG4 measurements should verify that their assays are fit for the clinical quality requirement of detection raised IgG4 levels and must verify the upper limit of their reference ranges and freedom from prozoning.


Beck S.C.,Peterborough And Stamfords Nhs Foundation Trust | Lock R.J.,Immunology and Immunogenetics
Annals of Clinical Biochemistry | Year: 2015

‘Measurement uncertainty of measured quantity values’ (ISO15189) requires that the laboratory shall determine the measurement uncertainty for procedures used to report measured quantity values on patients’ samples. Where we have numeric data measurement uncertainty can be expressed as the standard deviation or as the co-efficient of variation. However, in immunology many of the assays are reported either as semi-quantitative (i.e. an antibody titre) or qualitative (positive or negative) results. In the latter context, measuring uncertainty is considerably more difficult. There are, however, strategies which can allow us to minimise uncertainty. A number of parameters can contribute to making measurements uncertain. These include bias, precision, standard uncertainty (expressed as standard deviation or coefficient of variation), sensitivity, specificity, repeatability, reproducibility and verification. Closely linked to these are traceability and standardisation. In this article we explore the challenges presented to immunology with regard to measurement uncertainty. Many of these challenges apply equally to other disciplines working with qualitative or semi-quantitative data. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.


PubMed | Peterborough and Stamfords NHS Foundation Trust and Immunology and Immunogenetics
Type: Journal Article | Journal: Annals of clinical biochemistry | Year: 2014

Measurement uncertainty of measured quantity values (ISO15189) requires that the laboratory shall determine the measurement uncertainty for procedures used to report measured quantity values on patients samples. Where we have numeric data measurement uncertainty can be expressed as the standard deviation or as the co-efficient of variation. However, in immunology many of the assays are reported either as semi-quantitative (i.e. an antibody titre) or qualitative (positive or negative) results. In the latter context, measuring uncertainty is considerably more difficult. There are, however, strategies which can allow us to minimise uncertainty. A number of parameters can contribute to making measurements uncertain. These include bias, precision, standard uncertainty (expressed as standard deviation or coefficient of variation), sensitivity, specificity, repeatability, reproducibility and verification. Closely linked to these are traceability and standardisation. In this article we explore the challenges presented to immunology with regard to measurement uncertainty. Many of these challenges apply equally to other disciplines working with qualitative or semi-quantitative data.


PubMed | Clinical Biochemistry and Immunology and Immunogenetics
Type: | Journal: Annals of clinical biochemistry | Year: 2016

Faecal calprotectin has been shown to be a useful non-invasive marker for the diagnosis and monitoring of inflammatory bowel disease in children and adults. Although there are well-established reference ranges for the diagnosis of inflammatory bowel disease in adults, these have been less well studied in children. The objective was to establish reference ranges in our local population.All faecal calprotectin results from 2011 to 2014 were retrospectively collated and grouped according to patient age. Probability plots were used to determine expected upper limit of normal for each age group, and Mann-Whitney test was used to determine statistical difference between groups.Upper limit of normal for age groups 1-3.9 years, 4-17.9 years and 18 years plus were 77, 62 and 61g/g, respectively. There was a significant difference (P=0.0013) between the median calprotectin concentration for the age group 1-3.9 years (n=87) and 4-17.9 years (n=636) and between the age group 1-3.9 years and 18 years plus (n=7953, P=0.0001), but there was no significant difference between the age groups 4-17.9 years and 18 years plus (P=0.4206).In our local population, faecal calprotectin varies with age. Children aged 1-3.9 years had higher concentrations of faecal calprotectin than adults, but there was no significant difference in faecal calprotectin between older children and adults. This is in agreement with other published studies; however, the faecal calprotectin upper limit of normal calculated for children aged 1-3.9 years was lower than has been observed elsewhere.

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