the wild-type ␤-globin gene between the second nucleotide of codon 112 and the first nucleotide of codon 116 (Table 1). We hypothesized that ␤116(G18)His was deleted and the peptide sequence Arg-Val-Leu-Ala-His was inserted between ␤115(G17) and ␤117(G19) of the normal ␤-globin chain (Table 1). MALDI-TOF MS was performed on a tryptic digest of the ␤ X-globin chain to confirm this interpretation. The ␤ X-chain should contain 150 amino acid residues vs 146 for the normal ␤ A chain with a theoretical mass shift of ϩ439.29. Theoretical masses of tryptic peptides from ␤ X-and ␤ A-chains (8) were compared with the experimentally obtained peptide masses (Table 1). The experimentally obtained masses of different peptides were very close to their theoretical masses. The two tryptic peptides, ␤T12 and ␤T13, generated by the fiveamino acid insertion were characterized by MALDI-TOF MS (Fig. 1B). The present Hb variant was called Hb Antibes-Juan-Les-Pins and was associated with hematologic abnormalities: erythrocytes, 5.41 ϫ 10 3 /L; Hb, 137 g/L; mean corpuscular volume, 78 fL; and mean corpuscular Hb, 25.3 pg. The variant was also found in two children of the same carrier. They presented with the same hematologic abnormalities without iron deficiency. Oxygen dissociation curves performed after stripping with or without the addition of 2,3-diphosphoglycerate or chloride ions were normal. Among MS techniques for studying Hb variants, ESI-MS is the most frequently used and can be associated with peptide sequencing using tandem MS, but it often gives multiply charged fragment ions (4, 5). On the other hand, MALDI-TOF MS gives single-charge peptide ions and has been used for identification of some singlemutation Hb variants (9, 10). The present report shows that MALDI-TOF MS can be use to identify Hb variants. This MALDI-TOF peptide mass fingerprinting method is currently used in our laboratory for abnormal globin chains analysis. The presence of the 12-nucleotide repeat strongly suggests that the origin of this insertion is probably based on a slipped mispairing by DNA polymerase during replication. Such an explanation has been proposed for different Hb variants (11). Amino acid residues at positions ␤115-␤119 at the end of helix G in the normal ␤-globin chain are involved either in ␣1␤1 subunit links or externally on the Hb molecule (12). The insertion of five amino acid residues leads to the addition of a complete helix turn that has no effect on oxygen binding but decreases molecule stability.

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Background: The objective of this study was to evaluate the efficiency of free light chain (FLC) analysis in comparison to serum protein electrophoresis (SPE) for detecting M-proteinemia. Methods: A total of 553 consecutive patients for whom evaluation of M-proteinemia was requested were included in this study. For all patients, serum FLC analysis and SPE followed by pentavalent immunofixation analysis was performed. Identification of monoclonal bands was performed using specific antisera. FLC analysis was performed using the Modular P analyzer in accordance with the manufacturer's recommendations. Local reference ranges for FLCs on this platform were established based on samples from patients with a normal electrophoretic pattern wno monoclonal bands, no hypo-or hypergammaglobulinemia, no acute phase pattern and normal kidney function, i.e., estimated glomerular filtration rate (eGFR) )60 mL/minx. Results