Beta cell function: difference between revisions
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| 1 | {{Infobox concept | 1 | {{Infobox concept |
| 2 | | name = Beta cell function | 2 | | name = Beta cell function |
| + | 3 | | subtitle = Clinical assessment | |
| 3 | | Gold standard = Hyperglycaemic clamp with C-peptide deconvolution | 4 | | Gold standard = Hyperglycaemic clamp with C-peptide deconvolution |
| 4 | | Common surrogate = HOMA-B, insulinogenic index | 5 | | Common surrogate = HOMA-B, insulinogenic index |
| ⋮ | ⋮ | ||
| 18 | 19 | ||
| 19 | The stimulus matters as much as the analyte. Intravenous glucose isolates the beta cell from the gut; oral glucose or a mixed meal includes the [[Incretin effect|incretin]] contribution and therefore measures something closer to everyday physiology but confounded by gastric emptying. A study using an intravenous stimulus and one using a meal are not measuring the same construct. | 20 | The stimulus matters as much as the analyte. Intravenous glucose isolates the beta cell from the gut; oral glucose or a mixed meal includes the [[Incretin effect|incretin]] contribution and therefore measures something closer to everyday physiology but confounded by gastric emptying. A study using an intravenous stimulus and one using a meal are not measuring the same construct. |
| + | 21 | ||
| + | 22 | == Indices in common use == | |
| + | 23 | | Index | Stimulus | What it approximates | Principal weakness | | |
| + | 24 | |---|---|---|---| | |
| + | 25 | | HOMA-B | Fasting only | Basal secretory capacity | Ignores insulin sensitivity; unreliable at low fasting glucose | | |
| + | 26 | | Insulinogenic index | 0 and 30 min of OGTT | Early-phase response | Very sensitive to sampling time | | |
| + | 27 | | C-peptide index | Fasting C-peptide over glucose | Basal capacity | Confounded by renal clearance | | |
| + | 28 | | Disposition index | Clamp or OGTT | Secretion adjusted for sensitivity | Requires a sensitivity measure | | |
| + | 29 | | First-phase clamp | Hyperglycaemic clamp | Docked-vesicle pool | Labour-intensive, research only | | |
| + | 30 | ||
| + | 31 | The disposition index is conceptually the strongest of these because it embodies the hyperbolic relationship between secretion and sensitivity: for a given individual the product is approximately constant, and a fall in the product indicates genuine deterioration rather than compensation. Its practical weakness is that it inherits the error of both component measurements.{{r|bergman2002}} | |
| 20 | 32 | ||
| 21 | == References == | 33 | == References == |