Variation in GH and IGF-I assays limits the applicability of international consensus criteria to local practice

2.50
Hdl Handle:
http://hdl.handle.net/10541/70238
Title:
Variation in GH and IGF-I assays limits the applicability of international consensus criteria to local practice
Authors:
Pokrajac, Ana; Wark, G; Ellis, A; Wear, Joanne E; Wieringa, Gilbert E; Trainer, Peter J
Abstract:
BACKGROUND: There is increasing reliance on consensus criteria for decision making. Recent criteria state that acromegaly is excluded by a nadir GH during an oral glucose tolerance test (OGTT) of < 1 microg/l and a normal level of IGF-I. OBJECTIVE: To study GH and IGF-I assay performance close to cut-off values for active acromegaly. DESIGN AND METHODS: Two serum samples known to give borderline results were sent to all centres participating in the UK National External Quality Assessment Service (NEQAS). Sample A was assigned to be a nadir during an OGTT and sent for GH assessment to 104 centres. Sample B, with a clinical scenario, was sent to 23 centres that measure IGF-I, and these centres were asked to measure IGF-I, interpret the result and provide the source of their reference ranges (RRs). RESULTS: For sample A, the median GH was 2.6 mU/l (range 1.04-3.5 mU/l). Applying a conversion factor (CF) of 2.0 (1 microg/l = 2 mU/l), the most negatively biased method classified 10% of the values consistent with acromegaly, while the most positively biased method classified all values as consistent with the diagnosis. Applying a CF of 3.0 (1 microg/l = 3 mU/l), only 11% of results were consistent with acromegaly. For sample B, the median IGF-I was 50.8 nmol/l (range 24.3-60.9 nmol/l). All centres used age-related RRs. There was a 50% variation in the upper limit of the RRs between centres. Overall, 30% of the IGF-I results were against the diagnosis. There was little agreement in the RRs quoted by centres using the same method. CONCLUSION: Variability in assay performance, coupled with use of inappropriate CFs and RRs, undermines the applicability of international consensus criteria to local practice.
Affiliation:
Christie Hospital NHS Trust, Department of Endocrinology, Manchester, UK.
Citation:
Variation in GH and IGF-I assays limits the applicability of international consensus criteria to local practice. 2007, 67 (1):65-70 Clin. Endocrinol.
Journal:
Clinical Endocrinology
Issue Date:
Jul-2007
URI:
http://hdl.handle.net/10541/70238
DOI:
10.1111/j.1365-2265.2007.02836.x
PubMed ID:
17437512
Type:
Article
Language:
en
ISSN:
0300-0664
Appears in Collections:
All Christie Publications

Full metadata record

DC FieldValue Language
dc.contributor.authorPokrajac, Ana-
dc.contributor.authorWark, G-
dc.contributor.authorEllis, A-
dc.contributor.authorWear, Joanne E-
dc.contributor.authorWieringa, Gilbert E-
dc.contributor.authorTrainer, Peter J-
dc.date.accessioned2009-06-11T15:58:04Z-
dc.date.available2009-06-11T15:58:04Z-
dc.date.issued2007-07-
dc.identifier.citationVariation in GH and IGF-I assays limits the applicability of international consensus criteria to local practice. 2007, 67 (1):65-70 Clin. Endocrinol.en
dc.identifier.issn0300-0664-
dc.identifier.pmid17437512-
dc.identifier.doi10.1111/j.1365-2265.2007.02836.x-
dc.identifier.urihttp://hdl.handle.net/10541/70238-
dc.description.abstractBACKGROUND: There is increasing reliance on consensus criteria for decision making. Recent criteria state that acromegaly is excluded by a nadir GH during an oral glucose tolerance test (OGTT) of < 1 microg/l and a normal level of IGF-I. OBJECTIVE: To study GH and IGF-I assay performance close to cut-off values for active acromegaly. DESIGN AND METHODS: Two serum samples known to give borderline results were sent to all centres participating in the UK National External Quality Assessment Service (NEQAS). Sample A was assigned to be a nadir during an OGTT and sent for GH assessment to 104 centres. Sample B, with a clinical scenario, was sent to 23 centres that measure IGF-I, and these centres were asked to measure IGF-I, interpret the result and provide the source of their reference ranges (RRs). RESULTS: For sample A, the median GH was 2.6 mU/l (range 1.04-3.5 mU/l). Applying a conversion factor (CF) of 2.0 (1 microg/l = 2 mU/l), the most negatively biased method classified 10% of the values consistent with acromegaly, while the most positively biased method classified all values as consistent with the diagnosis. Applying a CF of 3.0 (1 microg/l = 3 mU/l), only 11% of results were consistent with acromegaly. For sample B, the median IGF-I was 50.8 nmol/l (range 24.3-60.9 nmol/l). All centres used age-related RRs. There was a 50% variation in the upper limit of the RRs between centres. Overall, 30% of the IGF-I results were against the diagnosis. There was little agreement in the RRs quoted by centres using the same method. CONCLUSION: Variability in assay performance, coupled with use of inappropriate CFs and RRs, undermines the applicability of international consensus criteria to local practice.en
dc.language.isoenen
dc.subject.meshAcromegaly-
dc.subject.meshBiological Markers-
dc.subject.meshConsensus-
dc.subject.meshGlucose Tolerance Test-
dc.subject.meshGrowth Hormone-
dc.subject.meshHumans-
dc.subject.meshInsulin-Like Growth Factor I-
dc.subject.meshReagent Kits, Diagnostic-
dc.subject.meshReference Values-
dc.subject.meshSensitivity and Specificity-
dc.titleVariation in GH and IGF-I assays limits the applicability of international consensus criteria to local practiceen
dc.typeArticleen
dc.contributor.departmentChristie Hospital NHS Trust, Department of Endocrinology, Manchester, UK.en
dc.identifier.journalClinical Endocrinologyen
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