Estimation of change limits (deltacheck) in clinical laboratory

Objectives Change limits, more commonly called delta check, are those in which a change in a patient’s measured result in relation to their corresponding preceding measurement is suspected of being erroneous and should be considered as a doubtful result. The aim of this study was to provide change limits for some biochemical and haematological quantities to detect doubtful measured results and to assess its effectiveness to detect erroneous results for their application in and the standardization of the plausibility control. Methods Change limits have been estimated for 13 biochemical and 6 haematological quantities. For each quantity, relative differences (D), expressed as a percentage between the two consecutive measured results from the same patient (from scheduled laboratory requests), were calculated. From these differences (D), the p5 and p95 percentiles of the data distribution were calculated. To assess the effectiveness of the change limits to detect laboratory errors, 43 erroneous laboratory reports, containing different biochemical and haematological quantities, were obtained from the standard laboratory plausibility control procedure. Results From the 43 erroneous laboratory reports, 31 (72%) were due to endovenous administration errors and 12 (28%) were due to mislabeling errors. All erroneous laboratory reports were detected when the change limits of the quantities were combined and applied together. Conclusions The best combination of quantities, which detect all the erroneous reports in the same specimen were: potassium, albumin, creatinine, glucose and haemoglobin.

Field Theory in Practice

The aim of this paper is to present K. Lewin’s Field Theory in practice, applying it to evacuation simulations. The construction of the field is discussed from the scratch in order to define the psychological space of a social event. Then, we illustrate the interplay of the physical and the psychological aspects of a mathematical model of human behavior presenting and discussing evacuation simulations of one event. At first we simulate the physical situation and then we calculate an evacuation time applying an elementary microscopic model. An empirical plausibility control is presented. When we apply mathematical modeling or cybernetic methods to social sciences we are said to be careful. Nevertheless, a social event might be considered, on a natural way, as a set of time series, from the point of view of statistics. In this paper we restrict ourselves to introduce probabilities of random variables associated to the physical and the psychological space and define a measure for the evacuation simulation: The entropy of the event, merging the physical and the psychological spaces.