title: A cause of falsely low HDL concentrations in HIV-infected patients: increased polyclonal serum immunoglobulin.
abstract: OBJECTIVE
  To describe the interference of polyclonal hypergammaglobulinemia in a direct HDL-c method.
  
  
  METHODS
  HDL-c was measured by a direct method (Roche Diagnostics) in four HIV-infected patients showing polyclonal hypergammaglobulinemia and also by precipitation with phosphotungstic acid and ultracentrifugation at a density of 1.063 kg/L. In addition, an electrophoretic lipid profile was performed by an automated electrophoretic system.
  
  
  RESULTS
  Direct HDL-c concentration was very low or even nondetectable in all hyperglobulinemic samples. Ultracentrifugation showed a higher HDL-c concentration, and the electrophoretic lipid profile showed a band corresponding to HDL particles whose cholesterol concentration was in concordance with that of ultracentrifugation. Kinetic monitoring of the absorbance for the direct HDL-c method showed a high reading after the first reagent addition and a final absorbance quite close to or even lower than the initial absorbance.
  
  
  CONCLUSIONS
  Although interference by any HIV therapy drug cannot be completely ruled out, our results showed that when high immunoglobulin concentrations existed in the patient's serum, the direct HDL-c method yielded low or undetectable HDL-c values. The high initial absorbance observed suggested an interaction between immunoglobulins and the first reagent of the method, producing a complex that scattered light and falsely decreased HDL-c concentrations.
authors.affiliation: Department of Biochemistry, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.
authors.forename: Edgar
authors.initials: E
authors.lastname: Zapico-Muñiz
authors.forename: Oscar
authors.initials: O
authors.lastname: Jorba-Castany
authors.forename: Rosa
authors.initials: R
authors.lastname: Bonet-Marqués
authors.forename: Jordi
authors.initials: J
authors.lastname: Ordoñez-Llanos
mesh_terms: D023241:Antiretroviral Therapy, Highly Active; D008076:Cholesterol, HDL / Q000097:blood* / Q000276:immunology; D015658:HIV Infections / Q000097:blood* / Q000188:drug therapy / Q000276:immunology; D006801:Humans; D007136:Immunoglobulins / Q000097:blood* / Q000276:immunology
chemical_list: D008076:Cholesterol, HDL; D007136:Immunoglobulins