Test strip for determining concentration of triglycerides
View Patent ↗A dry-phase triglycerides test strip that can be stored at room or elevated temperatures for several months without significant degradation in its effectiveness. The test strip includes a test membrane which receives plasma and forms a colored response in proportion to concentration of triglycerides in the plasma. The test membrane is impregnated with an aqueous solution containing lipoprotein lipase (LPL) and 4-aminoantipyrine (4AAP). The inventors have found that by reducing the pH of the impregnating solution to less than that of the recommended pH range for one of the key components (viz., less than pH 6.0), overall stability of the test strips was dramatically improved. The improvement in storage capability of these triglycerides test strips represents not just a difference in degree, but a difference in kind.
1. A method of providing a test strip for use in measuring the concentration of triglycerides in whole blood, said method comprising: (a) forming an aqueous solution for impregnating a test membrane, the solution containing lipoprotein lipase (LPL) and 4-aminoantipyrine (4AAP) and maintaining the pH of the aqueous solution less than pH 6.0; (b) impregnating the test membrane with the aqueous solution; and (c) assembling the test membrane and at least one other test layer into a test strip adapted to receive a quantity of whole blood.
2. The method of claim 1 , further comprising the step of storing the test strip at room temperature or above for at least twenty (20) weeks with the test strip remaining substantially stable.
3. The method of claim 2 , further comprising the step of storing the test strip at room temperature or above for at least forty (40) weeks with the test strip remaining substantially stable.
4. The method of claim 2 , further comprising, before step (a), the step of forming a citrate foundation and maintaining the pH thereof less than 6.0 and using the citrate foundation as a component of the aqueous solution.
5. The method of claim 4 , further comprising maintaining the pH of the citrate solution at about pH 5.6.
6. The method of claim 1 , further comprising in step (a) maintaining the final pH of the aqueous solution at about 5.9.