Unique characteristics of new complete blood count parameters, the Immature Platelet Fraction and the Immature Platelet Fraction Count, in dengue patients

Abstract

The advanced platelet parameters Immature Platelet Fraction and Immature Platelet Fraction Count have been implemented in clinical practice as measures of thrombopoietic activity, mainly in hematologic disorders that cause thrombocytopenia. The purpose of this observational study was to examine thrombopoiesis as reflected by these 2 new CBC parameters in patients infected with dengue. The study was conducted in infectious disease referral hospital in Metro Manila, the Philippines. We enrolled hospitalized patients at admission who were diagnosed with acute dengue or community acquired bacterial infection (CABI). Immature Platelet Fraction (IPF) and Immature Platelet Fraction Count were evaluated at admission and during hospitalization. A total of 606 patients were enrolled from May 1, 2017 to June 1, 2018. The participants consisted of 152 patients with dengue infection, 180 confirmed CABI, and 274 suspected CABI patients. At admission, the percent IPF (IPF%) of the patients with dengue was significantly higher than that of the confirmed CABI patients (median 3.7% versus 1.9%; p <0.001). In a time course evaluation, there was no significant difference of IPF% between the patients with dengue infection and the confirmed CABI patients in the febrile phase (median 1.9% versus 2.4%; p = 0.488), however, the IPF% of the patients with dengue infection increased to be significantly higher than that of the confirmed CABI patients in the critical phase (median 5.2% versus 2.2%; p <0.001). Our study elucidated the unique characteristics and time-course trends of IPF percent and number (IPF#) in the patients with dengue infection. IPF% and IPF# are potentially valuable parameters in dengue and further investigation is required for the optimal use in clinical practice.

Fig 1. Comparison of platelet, IPF% and IPF# among dengue, confirmed CABI, and suspected CABI groups at admission.

Horizontal lines show the median and interquartile ranges. (A) shows a comparison including all participants and (B) shows a comparison including only the subgroups with severe thrombocytopenia <50×10³/μL at admission. Comparison of dengue, confirmed CABI and suspected CABI groups were performed using Kruskal-Wallis test followed by the Dunn’s post hoc test with Holm adjustment. *: P<0.05, †: P<0.01, ‡: P<0.001. CABI: community acquired bacterial infection, IPF%: Immature Platelet Fraction, IPF#: Immature Platelet Fraction Count.

Fig 2. Time course trends of platelet parameters in each group from the first to tenth days of illness.

Box and whisker plots show the time course trends of platelet parameters in each group from the first to tenth days of illness. Boxes show the median and interquartile values, whiskers represent the upper and lower adjacent values and dots indicate outside values. The total numbers of evaluations included on each day are indicated on the X axis by each group. CABI: community acquired bacterial infection, IPF%: Immature Platelet Fraction, IPF#: Immature Platelet Fraction Count.

Fig 3. Comparison of platelet parameters among dengue, confirmed CABI, and suspected CABI groups by specific time-phases.

Box and whisker plots show the platelet parameters of dengue, confirmed CABI, and suspected CABI groups observed in specific time-phases: febrile phase (day 1 to 3), critical phase (day 4 to 6), and recovery phase (day 7 to 10). (A) shows a comparison including all participants and (B) shows a comparison including only the subgroups with severe thrombocytopenia defined as platelet nadir <50×10³/μl during hospitalization. Boxes show the median and interquartile values, whiskers represent the upper and lower adjacent values and dots indicate outside values. Comparison of dengue, confirmed CABI, and suspected CABI groups were performed using the Kruskal-Wallis test followed by the Dunn’s post hoc test with Holm adjustment. *: P<0.05, †: P<0.01, ‡: P<0.001. CABI: community acquired bacterial infection, IPF%: Immature Platelet Fraction, IPF#: Immature Platelet Fraction Count.

Fig 4. Comparison of platelet parameters between the severe and non-severe dengue thrombocytopenia groups by specific time-phases.

Box and whisker plots show the platelet parameters of the severe thrombocytopenia dengue group defined as platelet nadir <50×10³/μl during hospitalization and the non-severe thrombocytopenia dengue group defined to include all patients with a platelet nadir ≥50×10³/μl during hospitalization observed in specific time-phases: febrile phase (day 1 to 3), critical phase (day 4 to 6), and recovery phase (day 7 to 10). Boxes show the median and interquartile values, whiskers represent the upper and lower adjacent values and dots indicate outside values. The comparison between each pair of dengue subgroups were performed using the Mann Whitney test. *: P<0.05, †: P<0.01, ‡: P<0.001. IPF%: Immature Platelet Fraction, IPF#: Immature Platelet Fraction Count.