Background: Accidental sample mix-ups and the need for their swift resolution is a challenge faced by every
analytical laboratory. To this end, we developed a simple immunoblot-based method, making use of a patient's
characteristic plasma antibody profile to Escherichia coli (E. coli) proteins.
Methods: Nitrocellulose strips of size-separated proteins from E. coli whole-cell lysates were incubated with
patient plasma and visualised with an enzyme-coupled secondary antibody and substrate. Plasma samples of
20 random patients as well as five longitudinal samples of three patients were analysed for antibody band
patterns, to evaluate uniqueness and consistency over time, respectively. For sample mix-ups, antibody band
patterns of questionable samples were compared with samples of known identity.
Results: Comparison of anti-E. coli antibody patterns of 20 randompatients showed a unique antibody profile for
each patient. Antibody profiles remained consistent over time, as shown for three patients over several years.
Three example cases demonstrate the use of this methodology in mis-labelling or -pipetting incidences.
Conclusion: Our simple method for resolving plasma sample mix-ups between non-related individuals can be
performed with basic laboratory equipment and thus can easily be adopted by analytical laboratories.