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- Proinsulin:Insulin Ratio
Expected Turnaround Time
7 - 15 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Specimen Requirements
Specimen
Serum, frozen
Volume
1 mL
Minimum Volume
0.6 mL (Note: This volume does not allow for repeat testing.)
Container
Red-top tube or gel-barrier tube
Collection
Transfer the serum into a Labcorp PP transpak frozen purple tube with screw cap (Labcorp No. 49482). Freeze immediately and maintain frozen until tested. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.
Storage Instructions
Freeze; stable for 200 days. Stable at room temperature for six hours or refrigerated for 24 hours.
Patient Preparation
Under various protocols, the patient may be fasting and drawn, or fasting and drawn after a glucose load.
Causes for Rejection
Quantity not sufficient for analysis
Test Details
Use
The proinsulin:insulin ratio may be useful in managing type 2 diabetic patients. High basal proinsulin:insulin ratio in noninsulin-dependent diabetic patients may predict acute beta-cell dysfunction.
Limitations
Prolonged IV glucose challenges in normal and obese subjects can produce significant increases in proinsulin:insulin ratios. Plasma/serum must be frozen due to the lability of insulin.
Methodology
Enzyme linked immunosorbent assay (ELISA); chemiluminescence
References
Davis SN, Piatti PM, Monti L, et al. Proinsulin and insulin concentrations following intravenous glucose challenges in normal, obese, and noninsulin-dependent diabetic subjects. Metabolism. 1993 Jan; 42(1):30-35. 8446045
Roder ME, Porte D Jr, Schwartz RS, Kahn SE. Disproportionately elevated proinsulin levels reflect the degree of impaired B cell secretory capacity in patients with noninsulin-dependent diabetes mellitus. J Clin Endocrinol Metab. 1998 Feb; 83(2):604-608. 9467581
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 500757 | Islet Cell Dysfunction Group 1 | 500755 | Proinsulin by ELISA | pmol/L | 27882-0 | |
| 500757 | Islet Cell Dysfunction Group 1 | 503065 | Insulin | uIU/mL | 20448-7 |
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