RESUMEN
<p><b>BACKGROUND</b>The false positive in conventional syphilis serological test was found in patients with multiple myeloma (MM).</p><p><b>OBJECTIVE</b>To investigate the relationship between the M-protein of patients with MM and the false positive in conventional syphilis serologic test.</p><p><b>METHODS</b>The M-protein of 68 MM cases was typed with immunofixation electrophoresis and 68 cases of MM were screened with non-specific and specific syphilis serologic tests, then the samples with syphilic serological positive were chosen and confirmed with immonobloting test, finally the relationship between M protein of MM and the false positive of syphilis serological test were analysed.</p><p><b>RESULTS</b>Four out of 68 cases showed the positive in syphilis serological test and further were confimed to be false positive by immunoblotting test, the false positive rate was nearly 6%. The M-protein of MM patients in our hospital mostly possessed IgG, κ type, followed by IgA, κ type, light chain κ type. In general, κ : λ = 2.4 : 1. Among samples of 4 cases with syphilis serological positive 2 cases were of IgG and κ type, 1 case was of IgG, λ type, another 1 case was IgA, κ type.</p><p><b>CONCLUSION</b>The M-protein of IgG and IgA types in MM patients results in syphilis serological false positive reaction. The clinicians and laboratorial technicians should pay a great attention to screen the MM patients for the false positive syphilis serological test so as to avoid the misdiagnosis and subsequent embarassment.</p>