| ObjectiveFirst is to investigate the value of insulin release index (IRI) in biochemical diagnosis of insulinoma when the serum insulin levels were assayed by Microparticle enzyme immunoassay (MEIA). Next, the value of C-peptide index (CPI) in insulinoma was analyzed. Then the data and blood glucose profile detected by CGMS in insulinoma which confirmed by pathological examine after insulinoma-ectomy, were analyzed to investigate the value of CGMS in the diagnosis of insulinoma. The relation of inslinoma and vascular complication was explored.MethodsRetrospective the clinical data of 56 insulinoma patients who had been diagnosed and operated in the first clinical hospital of Zhengzhou university from January,2007 to October,2010. There're 24 insulinoma patients who had performed OCTT and CGM. Then the data of 36 patients who had been diagnosed as T2DM with vascular complication was collected during the same time, which the constitution of sex and age should be fit with insulinoma group. The data detected by CGMS were analyzed by CGMS software 3.0. The CGM data of the normal glucose modulated people in Shanghai was as control. And we mainly observed the IRI, CPI, serum insulin level, blood glucose fluctuation, the duration and times of hypoglycemia. SPSS 17.0 was applied to analyze the data. P<0.05 is indicated as significant difference.ResultsWhen the 56 insulinoma patients'blood glucose level were less than 2.8mmol/L, the blood glucose, serum insulin level and IRI is 2.14±0.6mmol/L,18.12±17.0uIU/ml and 0.48±0.42. The IRI is less than 0.3 in 18 patients(32%) and more than 0.3 in 38 patients(68%) of whom it is more than 0.4 in 28 patients(50%). The 95% lower limit of IRI in these 56 patients is 0.07. Here,10 patients'serum insulin levels were simultaneously assayed by RIA. The IRI assayed by RIA(8.56±9.53) is obviously higher than that assayed by MEIA(2.93±4.09) (P<0.05). In addition, we can learn that 24 cases of insulinoma were performed C-peptide assay with plasma insulin assayed when BG<2.8mmol/L. The CPI and IRI were 0.10±0.060 and 49±0.55, respectively. The coefficient of variation (CV) of CPI is 0.60 which is less than IRI (1.12). Furthermore, there are 16 patients who were performed 72-hours fasting test and it was positive in 13 patients and negative in 3 patients.Then, the OGTT and insulin releasing test of 24 insulinoma and 36 T2DM patients were contrasted:The peak of BG and insulin level arose at 30-60 min in insulinoma group, but at 120 min in T2DM group. The BG levels of insulinoma group are all lower than T2DM group (P<0.05), however, the insulin levels at 30 min and 60min are higher than T2DM group, and as well as the insulin area under the curve(IAUC) (P<0.01). Besides, the fast plasma glucose (FPG) of insulinoma group is less than control, the fast insulin level (FINS) is at the contrary (P<0.05). And, the IIOMA-IR between insulinoma and T2DM group has no significance (P=0.21). Further, the analysis about the CGM of these two group shows that:the 24h-MBG, SD, Min and Max in insulinomas are 4.82±1.75mmol/L,1.57±0.82mmol/L, 2.43±0.38mmol/L and 9.84±3.41mmol/L in turn. And they are 8.39±2.44mmol/L, 2.28±0.86mmol/L,4.37±1.75mmol/L and 13.59±4.11mmol/L in T2DM group respectively. The 24h-Min and MBG of insulinoma group are all lower than T2DM group (P<0.05). The difference of 24h-BG fluctuation in insulinomas and T2DM has significance, also (P<0.05).The contrast of CGM between insulinomas and normal glucose modulated people in Shanghai was performed. The 24h-Min and MBG of insulinoma group are both lower than control, however, the 24h-SD and Max blood glucose are higher than control(P<0.05).Besides, the maximum, mean and the BGF of 24 insulinoma patients are higher than in nighttime (P<0.05). But the minimum in the whole day has no obvious difference (P>0.1). And the continuing of hypoglycemia in insulinomas is 9.87±7.45h (40.8%±30.3%) in 24-h. The percentage of it is 55.4%±34.0% at nighttime which is higher than 33.0%±33.7% in daytime (P<0.05), but the hypoglycemia times between daytime (2.0±5.0) and nighttime (2.0±4.0) has no significance (P>0.1).At last, from the logistics regression analysis, you can find that the 30-min insulin level of insulin releasing test,the blood glucose area under the curve and HbAlc are the influential factor of the macrovascular complication. And the OR is 0.94,1.12, and 7.62 respectively. On the other hand, the 30-min blood glucose of OGTT, HbA1c and duration of disease can affect the microvascular complication. The OR is 1.23.1.44 and 1.13 respectively.Conclusions1 If the serum insulin level are assayed by MEIA when BG is less than 2.8 mmol/L, inslinomas can't be excluded when IRI<0.3.2 The value of CPI in biochemical diagnosis of insulinoma should be to think highly.3 A "normal" test result shouldn't completely exclude the diagnosis, although the sensitivity of the 72-h fast test is high and still plays an important role in the diagnosis of an insulinoma..4 It is helpful for the biochemical diagnosis of insulinoma to use CGMS.5 Maybe, the 30-min insulin level is relevant with that the vascular complications rarely follow insulinoma patients. |
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