TY - JOUR
T1 - K index is a reliable marker of intrathecal synthesis, and an alternative to igG index in multiple sclerosis diagnostic work-up
AU - Crespi, Ilaria
AU - Vecchio, Domizia
AU - Serino, Roberto
AU - Saliva, Elena
AU - Virgilio, Eleonora
AU - Sulas, Maria Giovanna
AU - Bellomo, Giorgio
AU - Dianzani, Umberto
AU - Cantello, Roberto
AU - Comi, Cristoforo
N1 - Publisher Copyright:
© 2019 by the authors. Licensee MDPI, Basel, Switzerland.
PY - 2019/4
Y1 - 2019/4
N2 - The K free light chain (K) index has been suggested as a reliable marker of intrathecal synthesis, despite the 2017 McDonald criteria for multiple sclerosis (MS) suggesting to “interpret with caution positive immunoglobulin G (IgG) index when testing for oligoclonal bands (OB) is negative or not performed”. The aim of this study was to compare the performance of K and IgG indexes for MS diagnosis and OB detection in a cohort of Italian patients. We enrolled 385 patients (127 MS, 258 non-MS) who had cerebrospinal fluid (CSF) analysis, including isoelectric focusing (IEF), to detect OB in the diagnostic work-up. Albumin, IgG and free light chains were measured by nephelometry and used to calculate IgG and K indexes. Although the two markers were highly related (r = 0.75, r2 = 0.55, p < 0.0001), the K index showed greater sensitivity and negative predictive value (versus the IgG index) for OB detection (97% versus 48% and 97% versus 71%) and MS diagnosis (96% versus 50% and 98% versus 78%). These results support K index (and not IgG index) as a first-line marker for MS, followed by IEF, according to a sequential testing approach in CSF analysis.
AB - The K free light chain (K) index has been suggested as a reliable marker of intrathecal synthesis, despite the 2017 McDonald criteria for multiple sclerosis (MS) suggesting to “interpret with caution positive immunoglobulin G (IgG) index when testing for oligoclonal bands (OB) is negative or not performed”. The aim of this study was to compare the performance of K and IgG indexes for MS diagnosis and OB detection in a cohort of Italian patients. We enrolled 385 patients (127 MS, 258 non-MS) who had cerebrospinal fluid (CSF) analysis, including isoelectric focusing (IEF), to detect OB in the diagnostic work-up. Albumin, IgG and free light chains were measured by nephelometry and used to calculate IgG and K indexes. Although the two markers were highly related (r = 0.75, r2 = 0.55, p < 0.0001), the K index showed greater sensitivity and negative predictive value (versus the IgG index) for OB detection (97% versus 48% and 97% versus 71%) and MS diagnosis (96% versus 50% and 98% versus 78%). These results support K index (and not IgG index) as a first-line marker for MS, followed by IEF, according to a sequential testing approach in CSF analysis.
KW - Cerebrospinal fluid
KW - Diagnosis
KW - Immunoglobulins
UR - http://www.scopus.com/inward/record.url?scp=85076154904&partnerID=8YFLogxK
U2 - 10.3390/jcm8040446
DO - 10.3390/jcm8040446
M3 - Article
SN - 2077-0383
VL - 8
JO - Journal of Clinical Medicine
JF - Journal of Clinical Medicine
IS - 4
M1 - 446
ER -