CLINICAL AND LABORATORY CHARACTERISTICS OF THE LATENT FORM OF POLYCYTHEMIA VERA.

A high level of hemoglobin and hematocrit is one of the most important laboratory indicators of polycythemia vera (PV). Nevertheless, in some cases, these indicators may be normal or below the norm. This form of the disease is called latent or masked PV (LPV). It has been found that thrombohemorrhagic complications (THC) are more common in LPV patients than in classic PV (CPV) patients. The relationship between JAK2 gene mutation allele burden, thrombocytosis, leukocytosis level and the occurrence of thrombosis during LPV was analysed in different studies. The results some of them were conflicted. It is also possible that this situation occurs due to the delay in diagnosis and treatment of patients with LPV.

Aim: investigate the laboratory and clinical features of the latent form of PV.

Materials and methods: An analysis of PV patients registered in 2019-2020 was conducted. Out of them patients with LPV were distinguished. During diagnosis of the disease, general blood analysis, trepanobiopsy and histological examination of bone marrow, molecular genetic examination of peripheral blood and bone marrow were performed. All numerical indicators obtained in the course of the research were statistically analyzed taking according to the modern recommendations. Indicators in the groups were arranged in the order of variation, and the average indicator, standard error of this indicator, confidence interval for the 95% confidence level (CI-confidence interval) were calculated for each order. For comparing the groups, the integrity criterion p was taken into account. Calculations were performed using ONE-WAY-ANOVA calculation software.

Results: We study 101 patients. Out of them 36 patients with latent polycythemia were identified. The clinical and laboratory parameters of patients with LPV and CPV were compared. In latent PV the complaints of patients were less intense; the size of the spleen was smaller; thrombotic complications were more often; hemoglobin, hematocrit, erythrocytes count was lower; the number of platelets was higher; leukocytes count and JAK2М617F gene allel burden were not statistically different. The most part of LPV patients, in contrast to CPV patients, was in a high-risk group of THC.

Conclusion: According to the obtained results, it can be concluded that timely and correct diagnosis of LPV is very important. Despite the fact that disease passes in a latent, masked form, THC are more likely to occur. This can be attributed to the high platelet count in the blood and the lack of timely treatment of the disease.