Agreement of Immunoassay and Tandem Mass Spectrometry in the Analysis of Cortisol and Free T4: Interpretation and Implications for Clinicians

Table 2

Pearson correlations of difference between methods versus MSMS alone, for Cortisol (𝑁=80). MSMS and (MSMS-IA) correlations reflect significant differences in the variances of the measurements by IA versus MSMS over time.

DIFFERENCE	Cortisol by MSMS,; 𝑇=0	Cortisol by MSMS,; 𝑇=30 min	Cortisol by MSMS,; 𝑇=60 min
𝑇=0 min, MSMS-IA	0.650 ∗
𝑇=30 min, MSMS-IA		0.494 ∗
𝑇=60 min, MSMS-IA			0.480 ∗

All Pearson correlation coefficients significant at 𝑃≤.001. ∗ indicates significant differences in the variances of the measurements by IA versus MSMS.