Reference intervals for mean platelet volume and immature platelet fraction determined on a sysmex XE5000 hematology analyzer.

BACKGROUND: New parameters describing the platelet population of the blood are mean platelet volume (MPV), which is a crude estimate of thrombocyte reactivity, and immature platelet fraction (IPF), which reflects megakaryopoietic activity. This study aimed to define reference intervals for MPV and IPF and to investigate whether separate reference intervals according to smoking status, age or sex are necessary. METHODS: Blood samples were obtained from subjects participating in The Danish General Suburban Population Study. MPV and IPF measurements were performed by the use of the Sysmex XE-5000 hematology analyzer. Reference intervals were established by a non-parametric method. RESULTS: In total, 1674 apparently healthy individuals (910 females and 764 males) were included. No significant age, sex or smoking status difference was observed. The reference interval was 9.6-13.1 fL for MPV and 1.3-9.0% for IPF, respectively. CONCLUSION: We have generated reference intervals for MPV and IPF in a large, adult Danish population and found those parameters remarkably stable across age, sex and smoking status.

Age- and sex-dependent reference intervals for D-dimer: evidence for a marked increase by age.

INTRODUCTION: A low D-dimer is commonly used to exclude venous thromboembolism in low risk patients. However, the reference intervals are poorly defined and D-dimer has been shown to increase by patient age. We aimed to establish age- and sex-dependent D-dimer reference intervals and to test the consequence of different cut-off limits. MATERIALS AND METHODS: By means of the STA-Lia test D-dimer was measured in 1,352 subjects aged between 23 and 93years from the general population. A further 94 subjects were measured with the HemosIL test. RESULTS: The reference intervals were age-dependent with the upper 95% limit increasing from 0.92 FEU mg/L in the age group <50years to 2.39 FEU mg/L in the group ≥70years. Minor differences in the reference intervals between sexes were found. The commonly used cut-off at 0.5 FEU mg/L resulted in a decrease of negatives from 91% in <50years to 56 % in ≥70years. The age-dependent cut-off value (patient's age*0.01 FEU mg/L in 50+ years) resulted in an increase of negatives by age. The linear increase in D-dimer has a slope at approximately 0.0077*age, meaning that a cut-off at (patient's age*0.0077) FEU mg/L, gives an almost constant number of positives across age groups. The two assays showed a poor correlation and a higher percentage of positives using the STA Lia test. CONCLUSIONS: The age-dependent increase in D-dimer seen in patients was confirmed, which questions the clinical value of the present cut-off for venous thromboembolism.