title: Detection of low level cryoglobulins by flow cytometry.
abstract: Several patients with cryoglobulin (CG) associated symptoms are seronegative for CG and other potentially causative biomarkers. We analyzed whether it is possible to detect cryoprecipitates by flow cytometry and whether the sensitivity of their demonstration can be increased as compared to visual inspection. Sera from 91 patients with suspected CG associated symptoms and 33 healthy controls were examined for the presence of CG by conventional visual testing and by flow cytometry for small diffracting particles. For calibration purposes we tested lipid micelle dilutions (positive controls) by both methods. The minimum concentrations of lipid micelles to be detected by visual inspection and flow cytometry were 128.5 and 2.0 pg ml(-1), respectively. Among the 91 patients and 33 controls, only 1 patient serum was positive for CG by conventional testing. This sample was also positive on flow cytometry. In the serum of a patient known to be positive for CG, laser diffracting particles were quantified by flow cytometry after keeping serum at 4°C for 3 days. Of the 91 patients, 14 additional samples displayed cold precipitates which redissolved after rewarming during flow cytometry. All 15 (1 + 14) patients positive for CG on flow cytometry suffered from symptoms usually associated with CG. Some precipitates were labeled with anti IgG and IgM antibodies confirming that the particles detected by flow cytometry contained immunoglobulins. No small diffracting particles were detected in the sera of the 33 healthy controls. Flow cytometry is equally specific but much more sensitive in the detection of CG than visual inspection.
authors.affiliation: Department of Internal Medicine 3, University of Erlangen-Nürnberg, Krankenhausstrasse 12, D-91054 Erlangen, Germany.
authors.forename: Rüdiger B
authors.initials: RB
authors.lastname: Müller
authors.forename: Birgit
authors.initials: B
authors.lastname: Vogt
authors.forename: Silke
authors.initials: S
authors.lastname: Winkler
authors.forename: Luis E
authors.initials: LE
authors.lastname: Muñoz
authors.forename: Sandra
authors.initials: S
authors.lastname: Franz
authors.forename: Peter
authors.initials: P
authors.lastname: Kern
authors.forename: Christian
authors.initials: C
authors.lastname: Maihöfner
authors.forename: Ahmed
authors.initials: A
authors.lastname: Sheriff
authors.forename: Johannes
authors.initials: J
authors.lastname: von Kempis
authors.forename: Georg
authors.initials: G
authors.lastname: Schett
authors.forename: Martin
authors.initials: M
authors.lastname: Herrmann
mesh_terms: D000888:Antibodies, Anti-Idiotypic / Q000097:blood; D002138:Calibration; D016022:Case-Control Studies; D003449:Cryoglobulinemia / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D003450:Cryoglobulins / Q000032:analysis* / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D008055:Lipids; D008297:Male; D008823:Micelles; D008875:Middle Aged; D012680:Sensitivity and Specificity
chemical_list: D000888:Antibodies, Anti-Idiotypic; D003450:Cryoglobulins; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D008055:Lipids; D008823:Micelles; C048844:anti-IgG; C044203:anti-IgM