The role of antibody indexes in clinical virology

Abstract

Background: Serological techniques are an essential part of the diagnostic tools used in clinical virology. Among these techniques, antibody indexes are not novel, but do require specific expertise. Their niche has expanded substantially in recent years due to increasing evidence of their performance to diagnose viral infections. Objectives: This narrative review describes the background and clinical applications of antibody indexes. The first objective is to provide an overview of the theoretical background, insights for implementation, limitations and pitfalls. The second objective is to review the available evidence for the diagnostic performance, with a specific focus on viral encephalitis and uveitis. Sources: A comprehensive literature search was performed in PubMed, including original studies and reviews, with no time limit on the studies included. The following search terms were used: antibody index, GoldmanneWitmer coefficient, Reibergram, viral encephalitis, viral uveitis, herpes simplex virus, varicella zoster virus, cytomegalovirus, EpsteineBarr virus, rubella virus, measles virus, enterovirus, influenza virus, flaviviruses. Content: Antibody indexes can support the diagnosis of a spectrum of viral infections in immune privileged sites such as the central nervous system and the eye, through the demonstration of virus-specific intrathecal or intraocular antibody production. This is especially useful in situations where PCR has a lower positivity rate: infections with rapid viral clearance due to natural immunity or treatment and chronic stages of viral infections. Implications: Antibody indexes expand the clinical microbiologist's diagnostic toolbox. Careful interpretation of the results of these assays is crucial and further standardization of methods is required to improve interchangeability of results between laboratories.

Antibody indices of infectious pathogens from serum and cerebrospinal fluid in patients with schizophrenia spectrum disorders

“…Some Als were < 0.7 and thus could not be measured optimally (cf. Figure 1) as known from other studies [43,47]. Finally, it must be mentioned that although the determination of pathogen-specific AIs entails many advantages, such as the detection of immunological responses in the CNS even years after pathogen contact or detection of polyspecific immune responses [47], it does not provide concrete information about infectious disease status or involvement.…”

Intrathecal Synthesis Index of Specific Anti- Treponema IgG: a New Tool for the Diagnosis of Neurosyphilis

“…S1 in the supplemental material. According to Reiber, a cutoff value of 1.4 should be used, whereas others suggested a cutoff value of 2 or 3 to demonstrate local pathogen-specific antibody production in CSF ( 30 , 31 ). Thus, we have established an AI cutoff to maximize the diagnostic performance of the test using receiver operating characteristic (ROC) curve.…”

Case Report: Unilateral Sixth Cranial Nerve Palsy Associated With COVID-19 in a 2-year-old Child

“…Of particular note in this context, SARS-CoV-2 specific IgG was also detected in CSF. Pathogen-specific antibody index as an indicator for potential intrathecal antibody production was negative, suggesting involvement of central nervous system being secondary to systemic infection rather than direct viral infection (14). An rRT-PCR for SARS-CoV-2 from CSF was negative.…”