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Salimetrics HS-Cortisol kit is a competitive immunoassay specifically designed for the quantitative in vitro diagnostic measurement of salivary cortisol. This kit may be used to measure adrenal cortical function and as a screen for Cushing's and Addison's disease. Saliva cortisol accurately reflects the amount of serum cortisol in the circulation. This kit is not intended for use with serum or plasma samples.

Device Description

Test Principle- A microtitre plate is coated with rabbit antibodies to cortisol. Cortisol in standards and unknowns compete with cortisol linked to horseradish peroxidase for the antibody binding sites. After incubation, unbound components are washed away. Bound cortisol peroxidase is measured by the reaction of the peroxidase enzyme on the substrate tetramethylbenzidine (TMB). This reaction produces a blue color. A vellow color is formed after stopping the reaction with sulfuric acid. Optical density is read on a standard plate reader at 450 nm. The amount of cortisol peroxidase detected is inversely proportional to the amount of cortisol present. The optical density readings of the calibrators are used to form a standard curve to which the optical densities of the controls and samples are compared.

Kit Description- The kit consists of an antibody coated 96 well plate, six calibrators at a concentration of 1.800, 0.600, 0.200, 0.067. 0.022, and 0.007 µg/dL of NIST(National Institute of Standards and Technology) cortisol, two controls representing a high (1.00 ug/dL) and low (0.100 ug/dL) level of salivary cortisol, the enzyme conjugate (1600X concentrate), assay diluent containing a pH indicator, wash buffer(10X concentrate), tetramethylbenzidine substrate solution, stop solution, and kit insert.

AI/ML Overview

Here's a breakdown of the acceptance criteria and study information for the Salimetrics HS Salivary Cortisol Enzyme Immunoassay Kit:

Acceptance Criteria and Reported Device Performance

The device's acceptance criteria are framed in comparison to a predicate device (Diagnostic Systems Laboratory Active Cortisol EIA, K850141), focusing on quantitative performance characteristics.

Characteristic	Acceptance Criteria (Predicate Device K850141)	Reported Device Performance (HS Salivary Cortisol EIA)
Intra-assay Precision	Coefficient of variation < 11%	Level 1: 4.3% (< 6% claimed)
		Level 2: 5.0%
		Level 3: 5.9%
		Level 4: 5.2%
Inter-assay Precision	Coefficient of variation < 12%	Level 1: 6.9% (< 11% claimed)
		Level 2: 8.6%
		Level 3: 6.7%
		Level 4: 10.6%
Sensitivity	0.1 µg/dL	<0.007 µg/dL
Linearity (Recovery)	81-119% recovery	84-105% recovery (Samples 1, 2, and 3 showed individual recoveries between 84.0% and 105.0% for various dilutions)
Recovery	93-124%	84-115% (Individual sample recoveries ranged from 84.1% to 115.2%)
Correlation with Serum	Not explicitly stated as a standalone criterion for the predicate, but the predicate is a serum assay.	r (64) = 0.89, p < 0.0001 (Saliva vs. Serum)
		Linear regression: y(serum µg/dL) = 5.177 + 15.132x(saliva µg/dL)
Specificity	No explicit numerical criterion given, but cross-reactivity data for various compounds in the predicate device for comparison.	Significantly lower cross-reactivity for several compounds compared to predicate. For example, Prednisolone: 9.530% for HS Salivary Cortisol EIA vs 58.3% for predicate.

Study Information

Sample Sizes and Data Provenance:
- Test Set:
  - Intra-assay Precision: 12 replicates for each of 4 levels (HS Salivary Cortisol EIA) and 3 levels (Predicate).
  - Inter-assay Precision: Mean of average duplicates for 12 separate runs for each of 4 levels (HS Salivary Cortisol EIA) and 3 levels (Predicate).
  - Sensitivity: 10 sets of duplicates at 0 µg/dL standard.
  - Linearity of Dilution: 3 saliva samples for HS Salivary Cortisol EIA, 2 samples for Predicate. Each diluted up to 1:16.
  - Recovery: 7 saliva samples for HS Salivary Cortisol EIA, 3 samples for Predicate.
  - Correlation with Serum: 68 matched samples (saliva and serum) from presumed normal adults.
  - Specificity: Tested various compounds at specific concentrations (e.g., up to 66,000 ng/mL for Transferrin).
- Data Provenance: Not explicitly stated (e.g., country of origin). The studies appear to be prospective, laboratory-based analytical performance studies conducted by the manufacturer. No indication of retrospective data or data from clinical sites is provided for these specific performance characteristics.
Number of Experts and Qualifications for Ground Truth:
- For the analytical performance studies (precision, sensitivity, linearity, recovery, specificity), ground truth is established by the known concentrations of calibrators, spiked samples, and controlled dilutions. This does not involve human experts in the way clinical diagnostic studies might.
- For the correlation with serum, the ground truth for serum cortisol measurements was established by the predicate device (Diagnostic Systems Laboratory Active Cortisol EIA). The "presumed normal adults" served as the source of samples, and their "normality" would be based on standard clinical criteria, but no specific number or qualification of experts establishing this normality is mentioned.
Adjudication Method: Not applicable for these analytical performance studies, as the ground truth is based on known values, reference methods (predicate device for comparison), or established analytical protocols.
Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study: No, this type of study was not performed. The submission focuses on the analytical performance of an immunoassay kit, not on the diagnostic performance of human readers with or without AI assistance.
Standalone (Algorithm Only) Performance Study: Yes, the entire submission describes the standalone performance of the HS Salivary Cortisol Enzyme Immunoassay Kit. It is a laboratory diagnostic device, and its performance is evaluated independent of human interpretation beyond the technical execution of the assay.
Type of Ground Truth Used:
- Analytical Ground Truth: For precision, sensitivity, linearity, and recovery, the ground truth is based on known concentrations of standards, controls, and spiked substances.
- Comparative Ground Truth: For correlation with serum, the predicate device (Diagnostic Systems Laboratory Active Cortisol EIA) served as the reference method for serum cortisol levels against which salivary cortisol measurements from the new device were compared.
Sample Size for Training Set: Not applicable. This device is an immunoassay kit, not a machine learning or AI algorithm that requires a training set in the conventional sense. The "training" of the assay refers to the internal calibration curve generated with the provided calibrators.
How Ground Truth for the Training Set Was Established: Not applicable. As it's an immunoassay kit, the concepts of "training set" and "ground truth for training" do not apply. The calibrators provided in the kit have NIST-traceable cortisol concentrations, establishing their "ground truth" for the assay's internal calibration.