Age- and sex-related variations in platelet count in Italy: a proposal of reference ranges based on 40987 subjects' data

PLoS One. 2013;8(1):e54289. doi: 10.1371/journal.pone.0054289. Epub 2013 Jan 31.


Background and objectives: Although several studies demonstrated that platelet count is higher in women, decreases with age, and is influenced by genetic background, most clinical laboratories still use the reference interval 150-400×10(9) platelets/L for all subjects. The present study was to identify age- and sex-specific reference intervals for platelet count.

Methods: We analysed electronic records of subjects enrolled in three population-based studies that investigated inhabitants of seven Italian areas including six geographic isolates. After exclusion of patients with malignancies, liver diseases, or inherited thrombocytopenias, which could affect platelet count, reference intervals were estimated from 40,987 subjects with the non parametric method computing the 2.5° and 97.5° percentiles.

Results: Platelet count was similar in men and women until the age of 14, but subsequently women had steadily more platelets than men. The number of platelets decreases quickly in childhood, stabilizes in adulthood, and further decreases in oldness. The final result of this phenomenon is that platelet count in old age was reduced by 35% in men and by 25% in women compared with early infancy. Based on these findings, we estimated reference intervals for platelet count ×10(9)/L in children (176-452), adult men (141-362), adult women (156-405), old men (122-350) and, old women (140-379). Moreover, we calculated an "extended" reference interval that takes into account the differences in platelet count observed in different geographic areas.

Conclusions: The age-, sex-, and origin-related variability of platelet count is very wide, and the patient-adapted reference intervals we propose change the thresholds for diagnosing both thrombocytopenia and thrombocytosis in Italy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Blood Platelets / cytology*
  • Child
  • Child, Preschool
  • European Continental Ancestry Group
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Italy
  • Male
  • Middle Aged
  • Platelet Count* / methods
  • Platelet Count* / standards
  • Reference Values
  • Sex Factors
  • Thrombocytopenia / blood
  • Thrombocytopenia / diagnosis*
  • Thrombocytosis / blood
  • Thrombocytosis / diagnosis*

Grant support

This study was supported by grants from: Italian Ministry of Education, University and Research (MIUR) n°: 5571/DSPAR/2002 (Ogliastra Genetic Park); MIUR-Programma Triennale di Ricerca (D. 1588), Pfizer Foundation, Rome and, “Instrumentation laboratory”, Milan (Moli-sani Project); MIUR-FIRB (RBIN064YAT), Assessorato Ricerca Regione Campania and Fondazione Banco di Napoli to MC (Cilento National Park); Compagnia di San Paolo, Torino, Fondazione Cariplo and, Ministry of Health, Ricerca Finalizzata 2008 to DT (INGI-VB); Ministry of Health and Department of Educational Assistance, University and Research of the Autonomous Province of Bozen/Bolzano and the South Tyrolean Sparkasse Foundation (South Tyrol); FVG Regional government, Fondo Trieste and the Ministry of Health (FVG and Carlantino). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.