What Is The Normal Blood Platelet Count – After Giulio Bizzozero identified platelets in the late 19th century, many authors attempted to define the normal concentration of these elements in human blood. However, platelet count methods were imprecise until the middle of the last century, and platelet counts ranged from 130-350 to 500-900 × 10/L of whole blood.2.

The development of Coulter’s principle in 1953 revolutionized hematology and led to the development of the electronic instruments currently used in our laboratories. About 30 years ago, these instruments were used to study thousands of blood samples from unselected donors, so the platelet count range was determined to be 150-450 or 150-400 × 10/L.4, 5 These values ​​are still in use today. Most Western countries, however, have shown that platelet counts vary by age, gender, and ethnicity during this process. Therefore, it is worth discussing whether a single reference interval is still valid for all people or whether a new normal range that takes these variables into account should be used in clinical practice.

What Is The Normal Blood Platelet Count

Age-related changes in platelets were investigated by Stevens and Alexander in 1977, who measured platelet counts in 868 blood donors aged 18 to 65 years and found no age-related differences. showed in 477 outpatients that the difference between children aged 1-5 years and elderly people over 71 years was more than 100 × 10/L.7 Correlation between platelet count. And age was found by a larger study that evaluated 12,142 adults in the United States and found statistically significant differences between younger and older adults.8 However, these differences were small: less than 30 × 10/L among 17-year-olds. – 19 years old and over 70 years old. That clears it up. An analysis of 12,517 inhabitants of the Sardinian geographic region found that a 10-year increase in age corresponded to a 9×10/L decrease in platelet count. The region includes 24, 318 subjects in 30 Molise cities and villages in the group of 10 and Molise projects. 11 Finally, a recent study pooled all data from subjects enrolled in the three aforementioned population-based studies to summarize the adolescent population. The associated changes were actually quite large: platelet counts in the elderly were reduced by 35% in men and 25% in women compared to those born prematurely. As shown in Figure 12, most of this reduction occurred during childhood and old age, with little change in adulthood. Thus, there is no doubt that age is a major determinant of platelet count in healthy individuals.

Transcriptomic Landscape Of Blood Platelets In Healthy Donors

There is no proven explanation for these age-related changes, although the precipitous decline in platelet counts during infancy may reflect a decline in vasculature from birth to adulthood. This has been suggested to be due to a survival advantage of subjects with low platelet counts or reduced blood stem cell reserves. 12 However, these two explanations are speculative and further investigation is required to clarify this issue.

Sex differences in platelets were first analyzed in 1977 in 868 blood donors. The mean platelet count was higher in men of all age groups, and although the difference was small (about 20-40 × 10/L), it tended to decrease after menopause. Later studies showed that women had slightly higher platelet counts. 7 , 8 , 14 The already mentioned studies on different Italian populations further support this conclusion and clearly define gender differences in ageing. 9-12 is not particularly different. Platelets were found in both men and women before age 15, whereas women had more platelets than men between 15 and 64 years of age and over 64 years of age.12 However, the sex difference in adults was only approx. 10% and associated with aging.

As for age-related variability, the mechanisms underlying sex differences in platelets are also unclear. However, the finding that females have higher platelet counts than males even after age 14 suggests that puberty is different. We can hypothesize that the decrease in body iron in women occurs during menstruation and continues in the elderly, 15 promoting the production of platelets. 16 , 17 However, hormonal differences between males and females after puberty also play a role. In particular, the observation that estrogen induces platelet formation in rats supports this hypothesis, although no data are available in humans.

Several studies have shown that platelet count is highly heritable, and several genetic factors responsible for platelet variability in healthy individuals have been identified. is isolated in Italy, where platelet counts range from 220 to 265 × 10/L in healthy residents of different regions. Ethnic-related disparities have been observed in the US population, and even more relevant disparities have been described in different African countries. 20

Complete Blood Count (cbc)

Figure 1. Platinum prevalence by age and sex of 40,987 residents in seven Italian regions. Platelet counts decrease with age, and women have more platelets after puberty. Modified with permission from Büno et al.12 (http://creativecommons.org/licenses/by/3.0/)

Figure 2. Age and sex-related changes in platelet count in 40,987 residents of seven Italian regions. Numbers in bars indicate reference intervals (2.5 and 97.5 percentiles) for world population estimates. The numbers outside the bars define the “extended reference range,” whose upper and lower limits define the upper and lower limits of the normal range for the mean platelet count and geographic region, respectively. Subjects with platelets within the reference range should be considered normal, and those with platelets outside this range but within the extended range are in the “grey” region, still consistent with a normal phenotype but also with mild thrombocytopenia. or angioedema. Reproduced with license (http://cre-ativecommons.org/licenses/by/3.0/) from Büno et al.

A number of observations in different populations suggest that age, sex, and genetic background in healthy individuals regulate platelet count. The effects of aging are greater than those of gender and ethnicity, but later changes may also be clinically relevant when combined with age changes. A good example is the geographic isolation of Sardinia, where different genetic backgrounds are responsible for large differences in platelet counts in different regions. Those with high platelet counts were less than 4% of those with low platelet counts. Conversely, more than 10% of the population over 60 years of age had a platelet count below 150 × 10/L, with the average platelet count falling to 4.5%, respectively. Thus, using 150–400 × 10/L as a normal range for platelets may put a population of elderly people in some areas at risk of being misdiagnosed with thrombocytopenia, while a younger population in other areas may be at risk. Misdiagnosis of hemangiomas.

The inappropriateness of a single cutoff of 150 × 10/L to define thrombocytopenia is also supported by the results of a five-year follow-up study in which 191 randomly detected platelet counts ranged from 100 to 150 × 10/L.21 In the vast majority of cases, levels of thrombocytopenia remained stable before any disease developed, and the authors concluded that patients in this category were at low risk of developing severe thrombocytopenia. Based on the above-mentioned evidence, we assume that these subjects (or a part of them) are completely healthy and have a platelet count below 150 × 10/L due to the joint action of sex, age and genetic background.

What Causes A High Platelet Count?

In conclusion, there is no doubt that a new reference range considering these variables would be desirable to detect more specific cases of platelet dysfunction. Indeed, such a tool was recently developed for the Italian population. 12 It shows the normal range of platelet counts under three age groups: under 15 years, 15 to 64 years, and over 64 years. Moreover, because sex-related differences occur after puberty, it implies separate values ​​for males and females in the latter two age groups. Finally, it defines an “extended reference interval” whose upper and lower limits are respectively the highest and lowest average platelet counts in the Italian region. This reference interval is shown in Figure 2.

Although the new reference interval is not yet used in clinical practice,

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