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8.2. Overview of commercial FLC assays

Chapter 8

A summary of the main commercial FLC assays that are currently being marketed is shown in Table 8.1.

Supplier Assay Antisera Method Instrumentation Specimen types Intended use Regulatory approval
Binding SiteFreelite Polyclonal (sheep) Latex-enhanced
immunoassay
Nephelometry,
turbidimetry
Serum, urine,
(plasma*, CSF*)
Diagnosis and
monitoring of MG, (detect intrathecal synthesis*)

FDA approved
CE-marked

Trimero DiagnosticsFree light chains kit Polyclonal Latex-enhanced
immunoassay
Nephelometry,
turbidimetry
Serum, urine Diagnosis of MG CE-marked
BiovendorHuman immunoglobulin
free light chains κ and λ ELISA
Monoclonal Sandwich ELISA Microplate reader Serum, plasma,
urine
Research only None
Abingdon HealthSeralite™-FLC Serum and Seralite-FLC Urine
(dual kappa and lambda tests)
Monoclonal Lateral flow
immunoassay
Test strip reader Serum,
urine
Diagnosis and
monitoring of MG
CE-marked
SiemensN Latex FLC Monoclonal Latex-enhanced
immunoassay
Nephelometry
Serum, plasma
(urine*, CSF*)
Diagnosis
of MM and AL
(monitoring of MG*, diagnosis of MS*)
FDA approved CE-marked
DiazymeHuman free light chain assay Polyclonal (κ: rabbit and goat; λ: rabbit) Latex-enhanced
immunoassay
Turbidimetry Serum
Diagnosis of MM CE-marked
FDA approved - for Hitachi 917 only
SebiaFLC Kappa and Lambda Polyclonal (rabbit) Sandwich ELISA Manual or automated Serum
Diagnosis and
monitoring of MG
CE-marked

Table 8.1. A summary of commercial FLC immunoassays. MG: monoclonal gammopathy; MM: multiple myeloma; AL: AL amyloidosis; MS: multiple sclerosis; ELISA: enzyme-linked immunosorbent assay; CSF: cerebrospinal fluid. * Specimen type or application is CE-marked but not FDA approved.

Freelite assays are latex-enhanced immunoassays that utilise sheep polyclonal antisera. They are the only FLC assays that are recommended by name in International Myeloma Working Group (IMWG) guidelines (Sections 8.7 and 25.3). By contrast, each of the other commercial FLC assays has features that may limit their usefulness. Trimero Diagnostics manufactures latex-enhanced immunoassays that are intended for use with serum and urine. However, to our knowledge, there are no peer-reviewed publications containing data of their assay's performance. There are also no publications on the use of the Diazyme human FLC assay, which only has regulatory approval for one turbidimetric instrument and has a very limited intended use. The Biovendor FLC assays are enzyme-linked immunosorbent assays (ELISAs). Whilst this assay format can achieve high sensitivity, they are intended for research use only. Sebia FLC assays are also based on an ELISA format, and are reported to produce results that are more coherent with those obtained by serum protein electrophoresis (SPE). However, use of SPE as the gold standard for light chain quantitation is debatable (Section 4.2.3).

Two commercial FLC assays intended for routine clinical use are based on monoclonal antibodies: Abingdon Health manufacture Seralite-FLC lateral flow FLC immunoassays [920] and Siemens supply N Latex FLC nephelometric FLC immunoassays [199]. A number of studies have concluded that values returned by monoclonal antibody-based FLC assays do not compare well with those returned by the polyclonal antibody-based Freelite assays. Of most concern is the fact that monoclonal antibody-based assays may fail to recognise a particular tumour-derived FLC clone, which can be detected by the Freelite assays. These and other issues are further discussed below.