Van Dalem Annelien, Demeester Simke, Balti Eric V, Keymeulen Bart, Gillard Pieter, Lapauw Bruno, De Block Christophe, Abrams Pascale, Weber Eric, Vermeulen Ilse, De Pauw Pieter, Pipeleers Daniël, Weets Ilse, Gorus Frans K
Diabetes Research Center, Brussels Free University-VUB, Brussels, Belgium.
Department of Clinical Chemistry and Radio-immunology, Universitair Ziekenhuis Brussel, Brussels, Belgium.
PLoS One. 2016 Dec 1;11(12):e0166702. doi: 10.1371/journal.pone.0166702. eCollection 2016.
The hyperglycemic clamp test, the gold standard of beta cell function, predicts impending type 1 diabetes in islet autoantibody-positive individuals, but the latter may benefit from less invasive function tests such as the proinsulin:C-peptide ratio (PI:C). The present study aims to optimize precision of PI:C measurements by automating a dual-label trefoil-type time-resolved fluorescence immunoassay (TT-TRFIA), and to compare its diagnostic performance for predicting type 1 diabetes with that of clamp-derived C-peptide release.
Between-day imprecision (n = 20) and split-sample analysis (n = 95) were used to compare TT-TRFIA (AutoDelfia, Perkin-Elmer) with separate methods for proinsulin (in-house TRFIA) and C-peptide (Elecsys, Roche). High-risk multiple autoantibody-positive first-degree relatives (n = 49; age 5-39) were tested for fasting PI:C, HOMA2-IR and hyperglycemic clamp and followed for 20-57 months (interquartile range).
TT-TRFIA values for proinsulin, C-peptide and PI:C correlated significantly (r2 = 0.96-0.99; P<0.001) with results obtained with separate methods. TT-TRFIA achieved better between-day %CV for PI:C at three different levels (4.5-7.1 vs 6.7-9.5 for separate methods). In high-risk relatives fasting PI:C was significantly and inversely correlated (rs = -0.596; P<0.001) with first-phase C-peptide release during clamp (also with second phase release, only available for age 12-39 years; n = 31), but only after normalization for HOMA2-IR. In ROC- and Cox regression analysis, HOMA2-IR-corrected PI:C predicted 2-year progression to diabetes equally well as clamp-derived C-peptide release.
The reproducibility of PI:C benefits from the automated simultaneous determination of both hormones. HOMA2-IR-corrected PI:C may serve as a minimally invasive alternative to the more tedious hyperglycemic clamp test.
高血糖钳夹试验是评估β细胞功能的金标准，可预测胰岛自身抗体阳性个体即将发生的1型糖尿病，但后者可能受益于侵入性较小的功能测试，如胰岛素原：C肽比值（PI:C）。本研究旨在通过自动化双标记三叶型时间分辨荧光免疫分析（TT-TRFIA）来优化PI:C测量的精密度，并将其预测1型糖尿病的诊断性能与钳夹衍生的C肽释放的诊断性能进行比较。
采用日间不精密度（n = 20）和分样分析（n = 95），将TT-TRFIA（AutoDelfia，珀金埃尔默公司）与胰岛素原（内部TRFIA）和C肽（Elecsys，罗氏公司）的单独检测方法进行比较。对49名高危多自身抗体阳性的一级亲属（年龄5 - 39岁）进行空腹PI:C、HOMA2-IR和高血糖钳夹检测，并随访20 - 57个月（四分位间距）。
胰岛素原、C肽和PI:C的TT-TRFIA值与单独检测方法的结果显著相关（r2 = 0.96 - 0.99；P<0.001）。TT-TRFIA在三个不同水平下PI:C的日间变异系数百分比更低（4.5 - 7.1 vs单独检测方法的6.7 - 9.5）。在高危亲属中，空腹PI:C与钳夹期间的第一相C肽释放显著负相关（rs = -0.596；P<0.001）（与第二相释放也相关，仅适用于12 - 39岁年龄组；n = 31），但仅在对HOMA2-IR进行标准化后。在ROC和Cox回归分析中，经HOMA2-IR校正的PI:C预测糖尿病进展至2年的效果与钳夹衍生的C肽释放相当。
PI:C的可重复性得益于两种激素的自动化同时测定。经HOMA2-IR校正的PI:C可作为更繁琐的高血糖钳夹试验的微创替代方法。
