The high frequency of false positive microbiological blood test results is a serious public health problem. In each case of reception of a preliminary positive response from the microbiology laboratory, the doctor is required to fill in the relevant documentation, to re-examine the patients and, possibly, to be hospitalized. Ultimately, efforts to confirm or refute previously obtained false positive results entail significant economic costs.

Despite the fact that implementing repeat venipuncture in children is difficult, it is worth it due to a significant decrease in the frequency of contamination of the resulting culture.

A study of patients from the Children's Medical Center admissions department (Ekron, Ohio, USA) under the supervision of admissions director N. Christopher showed that the contamination rate of the samples was significantly lower when blood was taken using new venipuncture compared to blood drawn via a recently installed IV catheter.

The results were unexpected. Some time before the study, the department observed an extremely high level of contamination of the blood samples and the measures taken to resolve this problem unfortunately did not succeed. To improve the situation, each nurse checked another during blood sampling, training programs on the technique of blood sampling were introduced, more attention was paid to the rules of asepsis and antiseptic. Researchers have attempted to reduce the number of repeat venipunctures by drawing blood through an installed IV catheter.

Before the study, if necessary, a blood catheter was inserted into the IV catheter, from which blood was drawn immediately after installation until it was connected to the system and the infusion started. through the catheter. During the I / O review, the catheter was installed only as directed. Blood samples were taken by puncturing different peripheral veins. In many cases, no IV catheter was placed at all and blood was drawn for microbiological examination using a standard venipuncture. In patients who have had an intravenous infusion, blood has been drawn using a second puncture. Despite the fact that the second venipuncture was associated with technical difficulties, the researchers suggested that this would reduce the frequency of contamination.

In total, the study evaluated 4,108 blood cultures (2,108 according to the standard methodology and 2,000 according to the new proposal) obtained from patients under 18 years of age.

All phlebotomies were performed by the sisters of the admission service. At the same time, the frequency of obtaining false positive results fell from 9.1% (blood draw according to the standard method) to 2.8% (blood draw by new venipuncture) (p less than 0.001). As a result, the frequency of false positive responses decreased by 70%.

Young age was associated with a high risk of contamination, regardless of the blood sampling method. Thus, the rate of contamination in patients before 12 weeks was 17%, while in children over 5 years - 4.5%. This is due to the fact that in young children, the blood sample is more difficult, since there can be only one corresponding vein.

It was also found that before, with a total false positive rate of 9.1%, the true positive rate was only 1.5%. When drawing blood using the proposed method, the frequency of truly positive results increased to 2.3%, however, the results were not statistically significant. A slight increase in the frequency of positive results could be due to a more selective approach to indications for blood sampling according to the new method, whereas previously, due to the simplicity of the method, the study was conducted for almost all patients.

In a recent article in the Journal of the American Medical Association, microorganisms isolated from blood cultures were classified as contaminants and pathogens. In controversial cases, the researchers consulted a doctor specializing in infectious diseases, while taking into account the demographic and clinical parameters of the patients. The presence of non-pathogenic bacteria, even single ones, in the blood samples indicated a violation of the venipuncture technique, and their detection in large quantities was considered as contamination. As a result, 26% of the outpatients examined were hospitalized with no confirmed bacteremia. False positive results have often led to an increase in the irrational administration of antibiotics. Furthermore, it is difficult to assess the moral damage inflicted on parents when they are informed of the false positive results of a blood test in children.

Despite the fact that there is some caution when drawing blood from two different veins in children, of all the methods offered, only this method can really reduce the frequency of false positive blood test results and the associated economic costs.