Valutazione del kappa index nelle patologie infiammatorie del sistema nervoso centrale nella popolazione pediatrica

AUTORI

ABSTRACT

Evaluation of the kappa index in inflammatory diseases of the central nervous system in a pediatric population

Introduction: the analysis of cerebrospinal fluid (CSF) and the determination of free light chains (FLC) are routinely used in the clinical laboratory. We investigated the utility of kappa index (Qkappa FLC/Qalb) as a specific biomarker for the differential diagnosis of multiple sclerosis and inflammatory neurological disorders in a pediatric population.
Methods: among 978 patients enrolled from January 2019 to May 2022, we analyzed 53 pediatric samples (0-17 years old). Albumin, IgG and kappa FLC in serum and CSF were measured by turbidimetric method, while isoelectrofocusing was performed to check for the presence of oligoclonal bands. The related CSF/serum indices (kappa index and IgG index) are also calculated.
Results: according to the clinical diagnosis, four groups of patients have been identified: multiple sclerosis, inflammatory neurological disorders, non-inflammatory diseases, negative controls. The kappa index cut-off of 6.2, obtained from our previous study, yielded 83.3% sensitivity and 85.7% specificity in the comparison between multiple sclerosis patients and the other groups. The IgG index (showing 50% sensitivity and 45.5% specificity at a threshold of 0.50) confirmed its poor diagnostic performance. In the comparison between inflammatory and non-inflammatory disorders a kappa index cut-off of 3.3 was associated with 80.6% sensitivity and 76.5% specificity.
Conclusion: the kappa index cut off (6.2) in use in our laboratory for multiple sclerosis diagnosis in the adult population can be confirmed in a pediatric cohort. Moreover, a lower kappa index cut-off (3.3) seems useful to discriminate pediatric inflammatory diseases, as recently reported by other Authors, and can be applied in the differential diagnosis of inflammatory processes of the central nervous system.

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