English 
Italian Il calcolo del kappa index come valida alternativa alla determinazione delle bande oligoclonali nell’iter diagnostico dei pazienti con sclerosi multipla
The Kappa Index as a valid alternative to oligoclonal bands determination in the diagnostic process of patients with multiple sclerosis
AUTORI
1Struttura Complessa Direzione Universitaria di Biochimica Clinica Azienda Ospedaliero Universitaria Ospedale Maggiore della Carità, Novara
2Struttura Complessa Laboratorio di Biochimica Clinica Baldi e Riberi Azienda Ospedaliera Universitaria Città della Salute e della Scienza di Torino
3Struttura Complessa Laboratorio Analisi, Azienda Ospedaliera S,S, Antonio e Biagio e C, Arrigo, Alessandria
4Divisione di Chirurgia Toracica IEO Istituto Europeo di Oncologia IRCCS, Milano 5Direttivo SIBioC Piemonte, componente Gruppo di Studio Proteine
ABSTRACT
The Kappa Index as a valid alternative to oligoclonal bands determination in the diagnostic process of patients with multiple sclerosis
ntroduction: the role of the kappa free light chains (KFLC) index in the diagnostic workup of multiple sclerosis (MS) is still a matter of debate.
Methods: 667 subjects from three reference laboratories have been enrolled, including 181 MS patients and 486 controls with other immune-mediated or non-inflammatory disorders. Serum and cerebrospinal fluid KFLC index, serum and cerebrospinal fluid albumin and IgG concentrations were measured on BNII nephelometer (Siemens Healthineers. Marburg. Germany), while oligoclonal bands (OCB) were detected by isoelettrofocusing on Hydrasys system (Sebia. Bagno a Ripoli. Italia).
Results: KFLC index was higher in MS than in controls [median (interquartile range – IQR) 76.56 (35.05) versus 17.99 (2,34), p <0.001]. A cut-off of 5.0 resulted in 93.9% (min-max 82.6-96.0) sensitivity and 77.4% (70.3-80.3) specificity, with positive and negative predictive values of 60.7% (41.4-69.3) and 97.2% (93.6-98.0), respectively. OCB assessment yielded 94.6% (87.9-96.5) sensitivity and 91.4% (86.6-94.8) specificity, with positive and negative predictive values of 87.5% (78.6-92.0) and 96.4 (93.6-98.0), respectively. The three laboratories showed similar results, making it possible to adopt common thresholds. The relatively low specificity of KFLC may be related to the characteristics of the control population, in particular to the percentage of subjects with inflammatory conditions associated with intratechal immunoreactivity.
Conclusions: an algorithm for the diagnostic management of MS could be suggested based on the KFLC index as screening test, followed by the detection of OCB, in case of a positive result. Future studies are needed to evaluate possible relationships between KFLC index, as a quantitative variable, and other clinical features of MS, such as severity of the disease and prognostic scores.