Clarification in the Point/ Counterpoint Discussion Related to Surface-Enhanced Laser Desorption/ Ionization Time-of-Flight Mass Spectrometric Identification of Patients with Adenocarcinomas of the Prostate

our upper reference limit for this fraction in all patients. Gelatin-based plasma substitutes are denatured collagens and thus contain complex mixtures of proteins (4 ). Differences in composition among products might explain the distinct migration patterns seen, as well as the different absorbances at the wavelengths used by the CZE instruments. The proteinaceous nature of these plasma substitutes produces both absorbance in the ultraviolet range and protein dye-binding, thus giving interference in CZE as well as in AGE (but to a much lesser extent, and even more anodal, including interference in the 2-fraction; see Table 1 in the online Data Supplement). Synthetic plasma substitutes are given mainly at times when serum electrophoresis is rarely indicated, e.g., during emergency fluid resuscitation or for intraoperative hemodilution (4 ). Moreover, gelatin-based products are rapidly eliminated with an estimated half-life of 2.5 h (5 ). In conclusion, gelatin-based plasma expanders may cause interference with serum protein electrophoresis (CZE and to a lesser extent AGE). With CZE these substances typically produce a (polyclonal-like) increase in the -/ -region. To avoid problems, instructions should be given not to collect samples for serum protein electrophoresis during the first hours after infusion of gelatin-based plasma substitutes.