In the first analysis to estimate the gap between global supply and demand of blood, scientists have found that many countries are critically short of blood, according to a modelling study published in The Lancet Haematology journal.
The World Health Organization (WHO) recommends that for every 1,000 people in any country, a target of ten to 20 donors is needed to provide adequate supplies. However, the new findings suggest this underestimates the real volume of blood needed for many countries, and the authors propose that donation targets should instead vary by country, according to the types of diseases that are most prevalent.
Blood transfusions save lives and improve health, and the WHO states that ensuring a safe and adequate supply of blood should be an integral part of every country's national health care policy.
"Other studies have focused on blood safety, such as the risk of transmitting infections such as HIV, but ours' is the first to identify where the most critical shortages lie, and therefore where the most work needs to be done by governments to increase donation, scale-up transfusion services and develop alternatives," says affiliate assistant Professor Christina Fitzmaurice from the University of Washington, USA. 
To calculate the availability of blood worldwide, the researchers used data from a WHO survey on transfusion practices between 2011 and 2013, to which 180 of 195 countries responded. To estimate how this compared to each country's needs, they calculated the amount of blood and blood products needed for 20 different medical conditions (based on US data between 2000 and 2014). They used the 2017 Global Burden of Disease study to see how prevalent each condition was in the USA and how much blood would be needed to provide a transfusion to every patient needing one. They applied these estimates to the varying prevalence of diseases in 195 countries, arriving at an ideal number of transfusions according to national disease burden. Any shortage was the difference between a country's supply and its need.
The total global blood supply was estimated to be around 272 million units. However, the total global demand in 2017 was approximately 303 million units - a shortfall of around 30 million blood units. Across the 119 countries with insufficient supply, the shortfall totalled more than 100 million units, which was equal to around 1,849 units per 100,000 people.
Lower income countries had relatively low demand compared to high-income countries, which can be attributed to a lower disease burden from injuries and chronic diseases. However, these countries were also estimated to have the greatest shortfalls in supply. The supply of whole blood and of the three components derived from it - red blood cells, platelets and plasma - therefore varied sharply between countries.
In most high-income countries, supply was able to meet demand. For example, Denmark was estimated to have the greatest supply of all three blood components with 14,704 blood product units per 100,000 people. In contrast, South Sudan had the lowest supply at 46 units per 100,000. South Sudan's needs were 75 times greater than supply (3,537 units needed per 100,000 people vs 46 units supplied per 100,000 people). Madagascar had the second greatest shortage, with demand outstripping supply by 26 times (3,568 units per 100,000 people needed vs 134 supplied). India had the largest absolute shortage, being short of nearly 41 million units in 2017 (52.5 million needed vs 11.3 million supplied).
The causes for blood transfusions also varied regionally. Demand in high-income countries was mainly caused by injuries and cardiovascular diseases. For example, in central Europe nearly 30% of transfusions were for treating injuries (1,716 units per 100,000), and over 20% were for cardiovascular diseases (1,283 per 100,000). In southern sub-Saharan Africa and Oceania, over 20% of transfusions were for respiratory diseases and tuberculosis (789 per 100,000 in southern sub-Saharan African and 858 in Oceania). In western, eastern, and central sub-Saharan Africa, over 10% of the total need was for nutritional deficiencies, including iron deficiencies (over 300 units per 100,000).
To meet demand in 2017, all 195 countries would have needed to exceed the WHO goal of 10-20 donations per 1,000 people. Assuming that around 1.5 units of blood components can be derived from a donation, 40 countries required more than 30 donations, while four in eastern Europe required more than 40 donations per 1,000 of the population.
"As more people are able to access care in low and middle income countries, the demand for blood transfusions will increase further, and - without financial, structural and regulatory support - will widen the gap we've uncovered between global supply and demand of blood," says Dr Meghan Delaney from the Children's National Hospital in Washington DC. 
The authors note that basing the ideal transfusion need on US inpatient practices could lead to an underestimate of true blood needs outside the USA, especially where neglected tropical diseases, malaria and maternal disorders are more severe. Different responses to treatments can also increase the demand for blood products, for example some HIV treatments are more likely to cause anaemia in populations with malnutrition.
Writing in a linked Comment, Professor Thierry Burnouf from Taipei Medical University, Taiwan, says: "This study is a reminder that a safe and sufficient blood supply is needed to manufacture unique cell-based or protein therapeutic products. Substantial differences in the availability, safety, and quality of blood still exist around the world. Although an integral part of the public health system, financial, organisational, and infrastructural reasons contribute to blood-derived and plasma-derived products as being neglected medicines in low-income and middle-income countries. Comprehensive strategies, through national and regional commitment, international cooperation, and transfer of technologies to blood establishments, can help fill the gap and strengthen local blood systems so that patient access to life-saving blood therapies gradually improves."
NOTES TO EDITORS
This study was funded by the National Institutes of Health. It was conducted by researchers from the University of Washington, the Children's National Hospital and The George Washington University School of Medicine and Health Sciences, USA.
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The Lancet Haematology