Influence of test results on clinical decision making

When interpreting laboratory tests it is useful to use the notion of "threshold of a clinical solution".Under the latter, mean the value of the laboratory result, in which immediate medical actions are necessary( Table).Usually these are the limiting values ​​that are guided by the confirmation or exclusion of certain clinical manifestations or when recording significant physiological effects that occur when a particular test value that normally participates in maintaining homeostasis reaches this value. In most cases, the values ​​given in the table reflect homeostasis disturbances, which are dangerous for the patient's life. For strictly physiologically controlled parameters of homeostasis in the body( potassium, sodium, etc.), the thresholds of the clinical solution are closely related to the reference intervals. The values ​​of the investigated parameter are above or below the reference limit and constitute the threshold of the clinical solution. It should be borne in mind that the thresholds of the clinical solution for many tests are relevant to several diseases.

Critical values ​​of the results of laboratory studies, in which immediate action is required, must be known to every clinician.

In addition to the above approaches for evaluating the results of laboratory research, it is necessary to remember the following fundamental principles.

■ Ranges of reference values ​​- statistical values ​​of 95% of the population, deviations from the range do not necessarily indicate a pathology. The results of the analysis can fit within the limits of the reference values, but they will be higher than the baseline( normal values) of the patient;so in some cases it is necessary to conduct a series of analyzes to get an idea of ​​the results.

■ Diagnosis is never based on the result of one study;it is necessary to establish a tendency to change the results obtained. Deviations in several indicators are always more reliable and significant than deviations of only one indicator. If the deviations in two or three tests are characteristic for this pathology, it is more likely to confirm the diagnosis than if a deviation of only one indicator is detected.

■ The greater the degree of deviation of the result from the reference value, the higher the probability of having a pathology or this indicates that the existing pathology is very significant.

■ Oster rule: if a patient is under 60, try to explain the pathological results with one reason, if this fails, then look for a second reason.

■ When receiving pathological results, repeated studies are needed to confirm and determine the trend of their changes;the most important aspect in such cases is the simultaneous conduct of intralaboratory quality control.

Fig. Algorithm for evaluating the results of laboratory tests( for example, establishing the cause of increased activity of alkaline phosphatase in the serum)

Fig. Algorithm for evaluating the results of laboratory tests( for example, establishing the cause of increasing the activity of alkaline phosphatase in the blood serum)

Table Critical values ​​of the results of laboratory studies requiring immediate action [Sacher RA, 1983]

Table Critical values ​​of the results of laboratory studies requiring immediate action[Sacher RA, 1983]

■ The results of laboratory tests obtained even in the best laboratories are not absolute( that is, they do not possess 100%specificity, PC), in any given case they can mislead the clinician.

If the presented approaches to the evaluation of the results of laboratory studies