Effect of specimen type on free immunoglobulin light chains analysis on the Roche Diagnostics cobas 8000 analyzer

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Table 5 Linear regression summary statistics of specimen comparisons^a

	Slope (95 % CI)^b	Y-intercept (95 % CI)^b (mg/L)	Correlation coefficient	95 % CI at lower MDL^c (mg/L)	95 % CI at upper MDL^c (mg/L)
EDTA vs. serum
Kappa	0.969 (0.950–0.988)	2.58 (1.54–3.64)	0.9954	4.8–6.8	20.4–22.4
Lambda	0.995 (0.986–1.003)	0.367 (0.127–0.608)	0.9992	5.8–6.3	26.3–26.7
κ/λ ratio	1.001 (0.982–1.021)	0.133 (0.066–0.199)	0.9957	0.33–0.46	1.73–1.84
Li-heparin plasma separator tube vs. serum
Kappa	1.081 (1.063–1.100)	0.64 (−0.38 to 1.67)	0.9964	3.2–5.2	19.4–22.5
Lambda	0.988 (0.981–1.000)	0.279 (−0.101 to 0.557)	1.0000	5.7–6.3	26.1–26.6
κ/λ ratio	1.175 (1.154–1.196)	−0.091 (−0.188 to 0.007)	0.9961	0.12–0.31	1.65–1.83

^aAnalysis uses Deming regression excluding outliers (see Table 4)
^b CI confidence interval
^c MDL medical decision limit: kappa, 3.3 and 19.4 mg/L; lambda, 5.7 and 26.3 mg/L; κ/λ ratio, 0.26 and 1.65