Table 5.
Impact of sex on the agreement between quantitative and qualitative methods for the determination of an intrathecal IgG synthesis. The “gold standard” of the cerebrospinal fluid (CSF)-restricted IgG oligoclonal bands was used to calculate: (i) concordance through the Cohen’s kappa, (ii) sensitivity, (iii) specificity, and (iv) positive and (v) negative predictive value. Multiple sclerosis (MS) subjects (cohort 1 and cohort 2 together) and patients with the clinically isolated syndrome (CIS) (cohort 3) were both analyzed as a whole and grouped by sex.
| IgG Index | Reiber’s Formula | |
|---|---|---|
| Values (95% CI) | Values (95% CI) | |
| MS patients (n = 340) | ||
| Kappa | 0.371 (0.284–0.458) | 0.331 (0.249–0.414) |
| Sensitivity | 0.6807 (0.6245–0.7321) | 0.6386 (0.5813–0.6922) |
| Specificity | 0.9273 (0.8274–0.9714) | 0.9273 (0.8274–0.9714) |
| Positive Predictive Value | 0.9798 (0.9492–0.9921) | 0.9785 (0.9460–0.9916) |
| Negative Predictive Value | 0.3592 (0.2849–0.4408) | 0.3312 (0.2617–0.4088) |
| MS males (n = 109) | ||
| Kappa | 0.307 (0.174–0.441) | 0.234 (0.110–0.359) |
| Sensitivity | 0.617 (0.5160–0.7089) | 0.5532 (0.4526–0.6496) |
| Specificity | 1.000 (0.7961–1.000) | 0.9333 (0.7018–0.9966) |
| Positive Predictive Value | 1.000 (0.9379–1.000) | 0.9811 (0.9006–0.9990) |
| Negative Predictive Value | 0.2941 (0.1871–0.4300) | 0.2500 (0.1552–0.3769) |
| MS females (n = 231) | ||
| Kappa | 0.407 (0.296–0.518) | 0.385 (0.279–0.518) |
| Sensitivity | 0.712 (0.6441–0.7716) | 0.6806 (0.6115–0.7426) |
| Specificity | 0.900 (0.7695–0.9604) | 0.925 (0.8014–0.9742) |
| Positive Predictive Value | 0.9714 (0.9288–0.9888) | 0.9774 (0.9358–0.9939) |
| Negative Predictive Value | 0.3956 (0.3013–0.4983) | 0.3776 (0.2879–0.4764) |
| CIS patients (n = 89) | ||
| Kappa | 0.143 (0.046–0.240) | 0.126 (0.039–0.213) |
| Sensitivity | 0.4815 (0.3760–0.5886) | 0.4444 (0.3412–0.5527) |
| Specificity | 1.000 (0.6756–1.000) | 1.000 (0.6756–1.000) |
| Positive Predictive Value | 1.000 (0.9103–1.000) | 1.000 (0.9036–1.000) |
| Negative Predictive Value | 0.16 (0.08337–0.2851) | 0.1509 (0.07852–0.2705) |
| CIS males (n = 32) | ||
| Kappa | 0.087 (−0.034–0.209) | 0.067 (−0.029–0.164) |
| Sensitivity | 0.4333 (0.2738–0.6080) | 0.3667 (0.2187–0.5449) |
| Specificity | 1.000 (0.1777–1.000) | 1.000 (0.1777–1.000) |
| Positive Predictive Value | 1.000 (0.7719–1.000) | 1.000 (0.7412–1.000) |
| Negative Predictive Value | 0.1053 (0.01870–0.3139) | 0.09524 (0.01692–0.2891) |
| CIS females (n = 57) | ||
| Kappa | 0.180 (0.042–0.317) | 0.168 (0.037–0.299) |
| Sensitivity | 0.5098 (0.3768–0.6414) | 0.4902 (0.3586–0.6232) |
| Specificity | 1.000 (0.6097–1.000) | 1.000 (0.6097–1.000) |
| Positive Predictive Value | 1.000 (0.8713–1.000) | 1.000 (0.8668–1.000) |
| Negative Predictive Value | 0.1935 (0.09187–0.3628) | 0.1875 (0.08890–0.3531) |
No differences were found between male and female MS patients for sensitivity and specificity of both the IgG index (Fisher’s exact test: p = 0.2597 and p = 0.5655, respectively) and Reiber’s formula (Fisher’s exact test: p = 0.0656 and p > 0.9999, respectively). CI, confidence interval.