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Chapter 8

In a total of six studies published to date, which incorporated approximately 80 LCMM patients, the Siemens N Latex FLC assays failed to detect abnormalities in six λ LCMM and one κ LCMM patients (Table 8.8) [175][201][209][923][952][219]. By comparison, the same six studies reported that all of these LCMM patients were correctly identified by the Freelite assays. The best described cohorts of confirmed cases of LCMM were included in the studies by Schneider and Hoedemakers [209][219] in which 3/26 of confirmed LCMM cases were not detected by the N Latex FLC assays. In contrast, an abnormal Freelite κ/λ sFLC ratio has been detected in all of 692 LCMM patients at diagnosis (Chapter 15). The recommendation that sFLC analysis plus serum electrophoresis constitutes a suitable primary screening protocol for monoclonal gammopathies [136][167] should, arguably, only be applied to FLC analysis with Freelite assays and not N Latex FLC or any other FLC assays, which are not validated in this context.

Study Total no. of
LCMM patients
Missed LCMM N Latex FLC Freelite
κ FLC
mg/L
λ FLC
mg/L
κ/λ ratio κ FLC
mg/L
λ FLC
mg/L
κ/λ ratio
Lock 2013 [201]n.s
(189 MM)
λ LCMM 19.5 59.7 0.33
Normal
4.66 6070 <0.01
Abnormal
λ LCMM 12.8 40.2 0.32
Normal
7.9 422 0.02
Abnormal
Hoedemakers 2011 [209]3 κ LCMM
6 λ LCMM
λ LCMM n.s n.s n.s
Normal
n.s n.s n.s
Abnormal
Schneider 2013 [219]17 LCMM λ LCMM n.s n.s 0.8
Normal
n.s n.s 0.02
Abnormal
κ LCMM n.s n.s 0.8
Normal
n.s n.s 1.89
Abnormal
Sabatino 2017 [952]

1 λ LCMM λ LCMM 16.5 23.0 0.71
Normal
9.14 818.8 0.01
Abnormal
Pretorius 2012 [175]n.s λ LCMM 29 84 0.35
Normal
18 464 0.04
Abnormal

Table 8.8. Summary of missed cases of LCMM by N Latex FLC assays. Patients were categorised as misclassified if the N Latex FLC assays reported a normal κ/λ ratio (n.s. = not stated).

References