Calcium2

The Calcium2 assay is an automated clinical chemistry test that measures calcium concentration in human serum, plasma, or urine using the ARCHITECT c8000 System. Calcium measurements are used to diagnose and treat parathyroid disease, bone diseases, chronic renal disease, and tetany.

Both subject and predicate devices use the Arsenazo III methodology and the same assay principle where Arsenazo III dye reacts with calcium in acid to form a blue-purple complex measured at 660 nm. The subject device is limited to the ARCHITECT c8000 System, while the predicate supported both AEROSET and ARCHITECT c8000. The subject device offers an extended measuring interval for urine (24.0–96.0 mg/dL) and improved lower limits of measurement (LoQ 0.4 mg/dL serum, 0.5 mg/dL urine versus 1.0 mg/dL predicate).

CLSI EP05-A3 (precision evaluation), CLSI EP17-A2 (detection capability), CLSI EP06 (linearity evaluation), CLSI EP07 (interference testing), CLSI EP09c (method comparison), and CLSI EP34 (dilution verification). Accuracy was traced to NIST SRM 956d reference material.

The subject device shares identical methodology (Arsenazo III), specimen types (serum, plasma, urine), intended use, and clinical indications with the predicate. Performance data demonstrate equivalent or superior analytical characteristics: precision studies show comparable within-laboratory and reproducibility metrics (%CV ≤2%), linearity across the claimed range (2.0–24.0 mg/dL), acceptable accuracy bias (-3.7% to -0.6%), minimal interference from endogenous and exogenous substances, and excellent correlation with the predicate method (r=1.00 for both serum and urine). The primary differences—restriction to c8000 platform and improved lower detection limits—represent enhancements that do not raise new safety or effectiveness concerns.