Abstract

BUCCINI, Graciela S.  and  WOLFTHAL, D.L.. Valores de corte para índices de insulinorresistencia, insulinosensibilidad e insulinosecreción derivados de la fórmula HOMA y del programa HOMA2: Interpretación de los datos. Rev. argent. endocrinol. metab. [online]. 2008, vol.45, n.1, pp.03-21. ISSN 1851-3034.

BACKGROUND: insulin resistance status is frequently evaluated through the HOMA-IR index, but there still is a widespread missunderstanding about its interpretation. β-cell status is evaluated through the %B (β-secretion). Still, there are very few papers regarding cut-off values for HOMA-IR and its associated indexes that arise from the original HOMA formula. Indeed, the need of evaluation IR as a main component of the Metabolic Syndrome as defined by the WHO committee (1999), led us to try to calculate the cut-off value for HOMA-IR in case Insulin is measured by MEIA (Abbott Laboratories). A single HOMA-IR value (as well as %S, %-Sensitivity) may come from different glucose-insulin pairs, so that in itself it provides little information, specially regarding β-secretory status. That lack of information must be assessed through %-B, which also comes from different combinations of glucose-insulin values. OBJECTIVE: The aims of this study are: 1º) To calculate the cut-off values for HOMA-IR, %-S, %-B, to be reported along with Insulin to the physicians, as obtained by HOMA-formula. 2º) To calculate the cut-off values for HOMA2-IR, %-B, %-S as provided by the HOMA2 Calculator. 3º) Considering that each value of HOMA or %-B may come from multiple combinations of glucose-Insulin pairs, to design a graphic in which a patients status migth be evaluated. METHODS AND RESULTS: 208 OGTT were performed according to WHO 1999 recomendations, 110 patientes and 98 controls. Statistics were calculated by using G. Reaven's criteria about upper and lower quartile among people under 30kg/m² BMI. Data calculated were: upper quartile for HOMA-IR: 2.64; for HOMA2: 1.67; lower quartile for %S: 37.8%, HOMA2-%S: 59.9%; lower quartile for %B: 67.6%, HOMA2-%B: 73.0%. Study and interpretation of the data: we can calculate the different pairs of data that converge onto a same value of HOMA-IR (table3); if we then plot on a graphic Insulin vs. Glucose those different points, we could see a curve ranging from "low glucose-high insulin" points to "high glucose-low insulin" others (Fig. 1). We can draw a curve for each HOMA-IR value, but for the evaluation it is enough if we take the cut-off value and some lower and higher ones (Fig. 4). The same can be done for each data of %-B (table 4); in this case, we obtain a straigth line with a positive slope; the highest the %B, the highest the slope. Just like before, we can plot the cut-off value for %B, and some lower and higher (Fig.5). If we plot all this curves in a unique Insulin vs. Glucose graphic (Fig. 6), then we can see that the intersection of both cut-off lines leaves on the graphic four zones (beyond the uncertainty zones undermentioned), (Fig. 7, 8). The position of the pair of data of a patient on the plot could allow to predict about his insulin-sensitivity and β-secretory status, in spite of β-cell pulsatility. CONCLUSIONS: Cut-off data were calculated for MEIA-Insulin: HOMA-IR (2.64), %B(67.6) y %S (37.8). For HOMA2-Calculator: HOMA-2: 1.67; HOMA2-%B: 73.0%; HOMA2-%S: 59.9%. Given the limited information provided by HOMA-IR alone e suggest that patient´s reports for the physicians include HOMA-IR as well as %S, in order to evaluate the β-cell status and try to predict β-claudication as early as possible before it takes place. Nonetheless, in the long-time-evaluation of a patient, the method of Insulin dosage should be, if possible, the same one.

Keywords : Insulin resistance; Insulin sensitivity; HOMA-IR; Cut-off; Beta-secretion.

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