Table 4.

Sensitivity, specificity, and positive and negative predictive values of different systems compared with HPLC based on system‐specific cutoff points

	ECL‐Roche	CLIA‐Diasorin	EIA‐DIAsource	RIA‐DIAsource
Sensitivity	92.1 CI: 86.1‐95.8	92.4 CI: 85.7‐96.2	90.1 CI: 83.7‐94.3	91.8 CI: 84.0‐96.1
Specificity	84.6 CI: 76.8‐90.2	83.5 CI: 75.7‐89.3	77.2 CI: 68.6‐84.1	67.2 CI: 58.1‐75.1
PPV	87.2 CI: 80.5‐91.9	83.9 CI: 76.3‐89.5	82.0 CI: 74.9‐87.5	68.7 CI: 59.9‐76.3
NPV	90.5 CI: 83.2‐94.9	92.2 CI: 85.3‐96.1	87.1 CI: 79.0‐92.5	91.3 CI: 83.1‐95.8

Vitamin D status based on circulating 25(OH)D concentration (nmol/L) for HPLC: sufficiency >38.55, insufficiency ≤38.55; ECL‐Roche: sufficiency >43.5, insufficiency ≤43.5; CLIA‐Diasorin: Sufficiency >30.0; insufficiency ≤30.0; EIA‐Diasource: sufficiency >51.2; insufficiency ≤51.2; RIA‐Diasource: Sufficiency >51.4; insufficiency ≤51.4.

To develop HPLC‐specific cutoff points, changes of serum iPTH in different concentrations of serum 25(OH)D were used. Using ROC analysis, these cutoffs were then employed to develop cutoff points for other systems.