Use of iSYS-IDS IGF1-Assay Normative Data as a STANDARD in the Diagnosis of Pediatric Growth Hormone Deficienc

Adel Djermane; Yasmina Ouarezki; Asmahane Ladjouze; Sakina Kherra; Kahina Mohammedi; Meriem Bensalah; Belaid Aitabdelkader; Hachemi Maouche

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ESPE Abstracts (2024) 98 RFC7.4

ESPE2024 Rapid Free Communications GH and IGFs (6 abstracts)

Use of iSYS-IDS IGF1-Assay Normative Data as a STANDARD in the Diagnosis of Pediatric Growth Hormone Deficiency

Adel Djermane ^1,2,3 , Yasmina Ouarezki ^1,2,3 , Asmahane Ladjouze ^1,3 , Sakina Kherra ¹ , Kahina Mohammedi ¹ , Meriem Bensalah ¹ , Belaid Aitabdelkader ^1,3 & Hachemi Maouche ^1,2

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¹Algiers University 1, Algiers, Algeria. ²Public Hospital, El Harrach, Algeria. ³Cytogenetics and Oncology Genetics Research Laboratory, Algiers, Algeria

Background: Analysis of insulin-like growth factor-I (IGF-I) is an important tool in the diagnosis of growth hormone deficiency. However, there are significant differences between IGF-I assays and normative data sets, which may have important clinical implications. The aim of this study was to investigate the difference in Z-scores between the iSYS-IDS reference values and the reference values for the IGF-I specific assay used in children.

Method: Z-scores IGF1 for all short children were calculated using normative data from specific assays (Immulite2000, Cobas, Liaison) and using normative IGF-I data for iSYS-IDS and IGF-1 iSYS adjusted SDS. We determined ROC curves to provide the best cut-off value for sensitivity and specificity. The area under the curve (AUC) with 95% confidence interval (CI) was analysed. Differences in Z-scores were analysed at relevant clinical decision points (-2 SDS).

Results: Samples of 685 (417 from males, 268 from females) IGF-1 were obtained from patients with GHD (n = 303) and GH-sufficient children (n = 382). The mean age was 6.74±2.62 years. We found a significant correlation between IGF1-SDS for all normative data, IGF-I ng/ml and maximum GH peak (P <0.001). Clinically relevant discordance between Z-scores at -2 SDS was found in 19% of all samples. ROC analysis showed an AUC for IGF1 specific assay of 0.63 (95% CI: 0.59 - 0.67), for IGF1 iSYS adjusted of 0.70 (95% CI: 0.67 à 0.74) and for IGF1 iSYS of 0.71 (95% CI: 0.67 à 0.75). For the IGF1 specific assay the best pair of sensitivity and specificity was found at ≤-2.01 SDS (Se 50.7%, Sp 70.1%). For IGF1 iSYS adjusted, the optimal cut-off value was ≤-1.95 SDS (Se 51.2%, Sp 83.5%). For IGF1 iSYS, the optimal cut-off was ≤2.25 SDS (Se 50.8%, Sp 83.0%). A multiple regression analysis shows a correlation with IGF1 iSYS-SDS (P <0.0001). Comparison of AUC shows a significant difference between iSYS-iDS, iSYS adjusted SDS and IGF1 specific assay (P <0.0001). No difference was found between iSYS-iDS and iSYS adjusted SDS.

Conclusion: Our study shows that the cut-offs of the IGF1 assay with iSYS-IDS normative data show a better discrimination between GH-sufficient children and children with GHD. Based on these results, we propose to use the iSYS-IDS IGF1 assay normative data set as a standard for the assessment of GH secretion in children with short stature, regardless of the device used.