[False positives in infectious serology : a rare issue that should not be ignored]

Although rare, false-positive results from infectious serology tests can mislead the practitioner and have harmful consequences for the patient. The causes are not always clear, but there are certain principles that are important to be aware of, and that help to interpret these diagnostic puzzles correctly. Similarities between different families of pathogens, the technical characteristics of the tests used, the use of therapeutic human immunoglobulins, the detection of vaccine-induced antibodies or even the detection of vaccine antigens themselves can cause non-specific reactions. This article uses examples from routine laboratory practice to illustrate the problem and draw the attention of the treating physician to this issue.