When hematocrit falls below 20% or the HgB falls below 7 g/dl, a patient may need a blood transfusion to survive. Transfusion transmitted infections (TTI ) are a concern, especially in regions where specific viruses, bacteria, and/or parasites may be prevalent.
Mechanism of Action
Exclusive use of non-remunerated, volunteer donors has proven to dramatically reduce the risk of TTI. The FDA estimates that written pre-donor questionnaires further reduce TTI prevalence in the donor pool by 90%. Nevertheless, it is recommended that all transfusion services perform serological screens on donor blood. In general, the screening tests are identical to those used for patient diagnosis. Depending on resources available, individual samples may be screened for multiple TTI s simultaneously or sequentially. Sequential screening takes time, but may save resources by running the least expensive screens first, throwing out reactive samples, and thereby reducing the number of more expensive tests performed. Pooling of donor blood for batch testing in order to further save costs has been a subject of debate, but is generally not recommended. The dilution inherent in pooling could potentially compromise screen sensitivity. While there are economies of scale in running large testing centers where automated equipment can run simultaneous high-quality screens on large sample volumes, centralized donor recruitment and transport logistics can more than offset these savings in some settings.
Current use in High-Resource Settings
Blood is available and widely used in clinical settings in high-resource settings. In general, blood banking is highly centralized in high-resource settings. In the US, 97% of blood comes from non-remunerated, volunteer donors who give blood in donation centers around the country. Donations are then refrigerated and sent to high volume screening facilities, some processing 275,000 units annually. In 2006, 1.2% US donor blood was discarded after screening. In the US, a single unit of donated red blood cells costs around $195 to process, $50-$60 of which is used for testing.
Application in Low-Resource Settings
The WHO has long advocated that all countries develop nationally coordinated blood services similar to those used in high-resource settings. The reality is that 80% of transfusion services in tropical Africa are hospital-based and rely on donors recruited from the patient’s family. When family members are not available, commercial (paid) donors are sometimes used, despite higher risk of infection. Screening is a major problem, and some estimate that 5-10% of African HIV transmission is through transfusions. These issues increase the danger and slow the process of needed blood transfusions in low-resource settings.