ECE2020 Audio ePoster Presentations Pituitary and Neuroendocrinology (217 abstracts)
The impact of variations in laboratory measurements of IGF-1 and random growth hormone on the classification of acromegaly disease activity status: Lessons from the UK Acromegaly Register Reference Laboratory
Bilal Bashir 1,2 , Safwaan Adam 1,2 , Philip Monaghan 2,3 , Zoe Plummer 4 , Natasha Archer 4 , John Ayuk 5,6 & Peter Trainer 1,2
1The Christie NHS Foundation Trust, Manchester, United Kingdom; 2Manchester Academic Health Sciences Centre, Manchester, United Kingdom; 3The Christie Pathology Partnership, Manchester, United Kingdom; 4Society for Endocrinology, Bristol, United Kingdom; 5University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom; 6University of Birmingham, Birmingham, United Kingdom
Background: The UK Acromegaly Register contains data for 2700 patients. IGF-1 and random growth hormone (GH) measurements are used for disease monitoring. The registry reference laboratory (RRL) uses the Immunodiagnostic systems (IDS)-iSYS immunoassay platform for GH and IGF-1. The RRL uses age- and sex-specific reference ranges for IGF-1. We compared IGF-1 and GH results fromlocal laboratories to those of the RRL (pre-defined as the Gold standard) to determine the extent of differences and the implications for classification of disease activity status.
Methods: Blood samples were separated for local (IGF-1 5 centres, GH 4 centres; Table 1) and paired RRL analysis. Controlled disease was defined for IGF-1 as below the upper-limit of the laboratory reference range and for GH as <1 mg/l. We calculated the RRL vs local assay correlation co-efficient and percentage bias and also compared respective disease activity status classifications between individual centres and the RRL.
Results: The total number of IGF-1 and GH measured were 277 and 121 respectively. Key results are summarised in Table 1.
| Centre | Analyser | No. of paired samples | Correlation with RRL | % bias | Number of discordantly elevated readings§(%) | Number of discordantly normal readings§(%) | |
| IGF-1 | |||||||
| 1 | Mediagnos-RIA-CTl | 39 | 0.97*** | + 11.2 | 1(3) | 9(23) | |
| 2 | Siemens-Immulite-Xpi-2000 | 45 | 0.91*** | +6.5 | 3(7) | 0 | |
| 3 | Siemens-Immulite-Xpi-2000 | 128 | 0.96*** | + 10.8 | 12(9) | 6(5) | |
| 4 | IDS-iSYS | 19 | 0.80*** | + 7.3 | 0 | 0 | |
| 5 | IDS-iSYS | 46 | 0.88*** | – 1.53 | 2(4) | 3(7) | |
| GH | |||||||
| 1 | Siemens-Immulite Xpi-2000 | 43 | 0.97*** | + 12.1 | 4(9) | 1(2) | |
| 2 | Siemens-Immulite Xpi-2000 | 40 | 0.83*** | + 8.31 | 1(3) | 3(8) | |
| 3 | Beckmen-Unicell | 16 | 0.92*** | – 15.2 | 0 | 0 | |
| 4 | Siemens-Immulite Xpi-2000 | 22 | 0.99*** | – 1.26 | 1(5) | 0 | |
| **P-value <0.001. 1Inter-laboratory differences in IGF-1 reference range despite same analytical platform. §RRL definition of disease activity status was considered as the Gold standard; an elevated result in the local laboratory was classified as normal in the RRL (discordantly elevated) or local result was deemed normal but regarded as elevated at the RRL (discordantly normal). | |||||||
Discussion: Our results show a relatively modest bias and strong correlation between local and RRL IGF-1 values. Consequently, differences in disease activity classification may predominantly represent inter-laboratory IGF-1 reference range variances. There were differences in the bias and accuracy of GH measurements (compared to RRL) of local laboratories even when utilising the same analytical platform. Further standardisation, traceability and commutability of assays and harmonisation of reference ranges might improve biochemical monitoring thereby potentially enhancing clinical decisions.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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