(155 days)
The diaDexus PLAC™ test is an enzyme immunoassay for the quantitative determination of Lp-PLA2 (lipoprotein-associated phospholipase A2) in human plasma, to be used in conjunction with clinical evaluation and patient risk assessment as an aid in predicting risk for coronary heart disease.
The diaDexus PLAC™ test is based on the principle of a sandwich enzyme immunoassay using two specific monoclonal antibodies. The assay system utilizes monoclonal anti-Lo-PLA2 antibody (2C10) for solid phase immobilization on the microtiter stripwells. The test sample is first diluted with the sample diluent and incubated at 2-8°C for 60 minutes. The diluted test sample is then allowed to react with the immobilized monoclonal antibody at 2-8°C for 90 minutes. The wells are washed with distilled water to remove any unbound antigen. A second monoclonal anti-Lo-PLA2 antibody (4B4) labeled with the enzyme horseradish peroxidase (HRP) is then added and reacted with the immobilized antigen at 2-8℃ for 60 minutes, resulting in the Lp-PLA2 molecules being captured between the solid phase and the enzyme-labeled antibodies. The wells are washed with distilled water to remove unbound labeled antibodies. The substrate, tetramethylbenzidine (TMB). is then added and incubated at 2-8°C for 20 minutes resulting in the development of a blue color. Color development is stopped with the addition of Stop Solution (1N HCl), changing the color to yellow. The absorbance of the enzymatic turnover of the substrate is determined spectrophotometrically at 450 nm using a standard microplate reader and is directly proportional to the concentration of Lp-PLA2 present. A set of Lp-PLA2 calibrators is used to plot a standard curve of absorbance (v-axis) versus Lp-PLA2 concentration in ng/mL (x-axis) from which the Lp-PLA2 concentration in the test sample can be interpolated. The standard curve is constructed using a point-to-point curve fit manually or by using appropriate calibration curve fitting software.
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Acceptance Criteria and Device Performance Study for diaDexus PLAC™ Test
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly state pre-defined acceptance criteria for the analytical performance characteristics. Instead, it presents the results of these performance tests as factual observations. For the clinical performance, the acceptance criteria are implicitly defined by demonstrating a statistically significant association between Lp-PLA2 and CHD risk across different models.
| Characteristic | Acceptance Criteria (Implied) | Reported Device Performance |
|---|---|---|
| Analytical Performance | ||
| Analytical Sensitivity (Detection Limit) | A low detection limit suitable for intended use. | 1.2 ng/mL |
| Linearity (Dilution) | Percent recovery close to 100%. | Average recovery of 104% (range 133-1310 ng/mL) |
| Linearity (Dilution) | Percent recovery close to 100%. | Average recovery of 104% (range 79-982 ng/mL) |
| Antigen Recovery | Mean recovery close to 100% (with an acceptable range). | Mean recovery of 109% (range 97-119%) |
| Interfering Substances | No appreciable interference from common endogenous substances. | No appreciable interference for hemoglobin, triglycerides, cholesterol, bilirubin, and albumin at specified levels. |
| Precision (Intra-assay) | Low Coefficient of Variation (CV). |
§ 866.5600 Low-density lipoprotein immunological test system.
(a)
Identification. A low-density lipoprotein immunological test system is a device that consists of the reagents used to measure by immunochemical techniques the low-density lipoprotein in serum and other body fluids. Measurement of low-density lipoprotein in serum may aid in the diagnosis of disorders of lipid (fat) metabolism and help to identify young persons at risk from cardiovascular diseases.(b)
Classification. Class II (performance standards).