[Clinical thermometry--theory and critical approach]

The assessment of fever is complex. It must not only focus on the patient in question. Rather, as a first factor to be considered, clinical thermometry has its technical and methodological problems. Every method has its own pitfalls. Second, any assessed body temperature reflects a "local" body temperature which, again, is affected by many factors. In addition, physiological set points of normal body temperature vary among individuals, and, even in a given individual, body temperature has its physiological variations. In all, intra- and interindividual variabilities in measured "normal" body temperature are large (< 2 degrees C) which makes it difficult to define normality. No question, all the factors mentioned are equally involved when body temperature is assessed in the febrile patient. Results (particularly those of tympanic measurements) may be deceptive and must be interpreted with scrutiny in the broad context of the patient assessment. In adults, fever should be measured by the sublingual method, in the non-cooperating patient, in the newborn and in toddlers rectally.