La determinazione delle catene leggere libere nel liquido cefalorachidiano: l’esperienza di due laboratori italiani

AUTORI

ABSTRACT

Quantitation of immunoglobulin free light chains in cerebrospinal fluid: the experience of two Italian laboratories

The detection of oligoclonal IgG bands in cerebrospinal fluid (CSF) by isoelectricfocusing and immunodetection is the current “gold standard” method to detect an inflammatory process in central nervous system. However, as this test is time consuming and subjective, some authors have tested the measurement of free light chains (FLC) in CSF using a specific automated polyclonal antibody-based assay (Freelite, The Binding Site) with promising results. Recently, another automated nephelometric monoclonal antibody-based assay for FLC has been made available (N Latex FLC, Siemens). In our laboratories, we tested FLCk and l in CSF and serum using both assays. To test sensitivity and specificity, multiple sclerosis (MS) patients and non inflammatory neurological disease (NIND) patients as controls were selected. Both laboratories found statistically significant (P <0.05) difference between results in two groups. Using Freelite, the first laboratory defined the best cut-offs to discriminate between MS and NIND by ROC curves: i.e., 0.56 mg/L for FLCk, 7.82 for FLCk index, 0.31 mg/L for FLCl and 4.36 for FLCl index. Using N Latex FLC, the second laboratory estimated cut-offs by means of the NIND patients highest interquartile value, resulting in 0.22 mg/L for FLCk, 2.72 for FLCk index, 0.15 mg/L for FLCl and 2.07 for FLCl index. Sensitivities found with Freelite assay were 95% for FLCk index, 83% for FLCl index and 100% when both tests were considered. With N Latex FLC assay sensitivities were 100% for FLCk index and 93% for FLCl index. In both centers, isoelectricfocusing had 97% global sensitivity for MS. Our results show that, with both evaluated methods, CSF FLC can support or even replace isoelectricfocusing in clinical laboratories.

BIBLIOGRAFIA