Diagnostic Accuracy of Csf β2M Compared To Total Proteins in Neonates

Abstract

The diagnosis of CNS infections may be difficult in neonates. CSF shunt infections may be particularly difficult to assess .Objectives: (1) to compare the diagnostic accuracy ofβ2-microglobulin (β2m) vs total proteins in the CSF, in neonates with suspected CNS infections; (2) to determine the value of CSFβ2m in the diagnosis of CSF shunt infections .Methods: Neonates were included prospectively if a lumbar puncture was performed as part of a sepsis or meningo-encephalitis work-up. β2m was measured by enzyme immunoassay; total proteins by nephelometry. Results: 105 neonates without CSF shunts were studied: 30 had CNS infection (13 bacterial meningitis, 11 viral, 6 congenital meningo-encephalitis), and 75 did not. Areas under the ROC curve were: β2m 0.95±0.02 (cut-off value 2.5 mg/L), and total proteins 0.84±0.05 (cut-off value 100 mg/dL). β2m showed higher sensitivity and positive predictive value than proteins (97 vs 78, and 92 vs 54, respectively, p<0.001). In addition, 10 infants with CSF shunt were studied; 4 had infection. β2m was higher in infants with infection around the time of clinical suspicion (6.1±1.75 vs 3.1±1.04 mg/L, p<0.01), and β2m levels tended to increase 2 to 5 days after (10.2±0.97 vs 6.1±1.75,p=0.06). Conclusion: β2m showed a high diagnostic accuracy, with higher specificity and positive predictive value than total proteins. Total proteins had a lower area under the ROC curve, although the difference was not statistically significant.β2m in the CSF might be a useful ancillary tool in the diagnosis of neonatal CNS infection, including infants with CSF shunts.