Hospital-acquired anemia (HAA) is a condition where a patient who was not anemic at hospital admission becomes anemic during their hospital stay. This illness is also called iatrogenic anemia (anemia caused by medical examination or treatment) because of its association with frequent blood draws for diagnostic testing. HAA can increase the risk of surgical complications, infection, heart attack, stroke, and cancer progression or recurrence, lengthen hospital stays, and increase admission to the critical care unit and mortality.
The degree of diagnostic blood loss depends on the hospital’s practices and the length of a patient’s stay. Approximately 40 percent of non-anemic patients will develop HAA within 24 hours of admission to the intensive care unit (ICU). A study of patients who were being treated in the ICU for heart attack demonstrated that those who developed HAA had more blood drawn for diagnostic tests on average than those who did not develop HAA. The same study showed that for every 50 mL of blood drawn, there was an 18 percent increase in the risk for developing HAA.
There are several approaches that clinical laboratories can follow to mitigate diagnostic blood loss and reduce the prevalence of HAA.
Limiting laboratory tests
Laboratory tests provides valuable information that can help improve how patients are treated. But the costs of blood loss and the benefits of information need to be carefully weighed when ordering laboratory tests. Physicians should audit each test, assessing whether it will affect how the patient is treated and whether an appropriate amount of blood is being drawn.
Making use of clinical decision support tools can help laboratories identify unnecessary tests. One such tool was tested in a research study at a US Government Veteran Affairs Hospital from 2012 to 2014. The laboratory expert system (LES) is a software that enables laboratories to limit the number of redundant tests being performed by defining how often tests or test panels can be ordered for any patient. Implementing this system led to an 11.2 percent decrease in test volume per year with no adverse outcomes for patients reported and no increase in the mean length of stay for patients.
Using smaller collection tubes
Blood drawn for laboratory tests typically far exceeds the amount required to conduct the test. A comprehensive study of 140 institutions showed that laboratories collected a higher volume of blood than could be analyzed by their instruments including a median of 8.5 times more blood for routine complete blood cell counts and a median of 12 times more blood for routine electrolyte panels. These large sample volumes add up over time, contributing to a patient’s risk of developing HAA.
One solution to limit blood sample volume and mitigate the risk of HAA is to use small volume collection tubes when drawing blood samples for laboratory tests. In one study, researchers compared conventional-volume phlebotomy tubes (CVPT) and small-volume phlebotomy tubes (SVPT) for patients admitted to the surgical intensive care unit. Overall daily blood volumes drawn in the ICU significantly decreased from 31.7 mL when CVPTs were used to 22.5 mL when SVPTs were used. The researchers also reported fewer cases of anemia in patients where SVPTs were used for blood draws compared with patients where CVPTs were used.
Using closed blood sampling devices
The blood draw itself can waste patient blood. When drawing blood from an intravenous catheter, it must first be flushed with saline to clean out the line. A “waste” blood sample must then be drawn to remove all the saline and prevent sample contamination when collecting blood for laboratory testing. Each time this is done, patients lose between 0.5 and 3 mL of blood unnecessarily.
Using a closed blood sampling device can limit the amount of blood wasted when samples are drawn from patients. These systems have a separate reservoir where the blood taken for a waste sample is held until the required laboratory sample has been collected from the patient. Rather than being discarded, this waste sample can then be reinjected from this reservoir into the patient to prevent unnecessary blood loss.
A review of several studies suggested that using closed blood sampling devices could reduce blood loss by about 25 percent compared to patients with conventional arterial pressure monitoring systems. These devices can also prevent infections by minimizing the exposure associated with open sampling ports.
Performing point-of-care testing
Point-of-care testing (POCT) at the bedside offers an alternative to traditional laboratory testing. Devices used for POCT require smaller volumes of blood than traditional laboratory diagnostic tests, reducing diagnostic blood loss and the risk of developing HAA. As an added advantage, these devices reduce the time it takes to obtain results by eliminating time-consuming steps such as specimen transport, sample analysis, and data entry. Instead, physicians can see the results almost instantly and obtain relevant patient information. This technology is especially useful when a patient’s status is constantly changing, allowing physicians to respond better and in a timely manner.
Most research investigating the role of POCT in reducing the risk of HAA has been done in neonatal environments. In a study conducted by the Stanford University School of Medicine, researchers investigated whether using a point-of-care iSTAT analyzer to measure a variety of blood indicators would reduce the number and volume of red blood cell transfusions required in the first two weeks of life for infants born prematurely. They found a 46 percent reduction in the number of transfusions performed and a 43 percent reduction in the volume of transfusions after the POCT was implemented.
Using more than one of these approaches is likely to have the greatest impact on limiting the risk of HAA. One meta-analysis suggested that combining more than one intervention can result in a 70 percent reduction in the amount of blood lost by adult patients in the ICU.
As new technologies are adopted by clinical labs, the volumes of blood needed for laboratory diagnostic tests will likely continue to go down. Automation will increasingly play a role in reducing laboratory errors, limiting the need for repeat tests, and conserving patient blood samples. Greater usage of multiplex assays will mean more than one parameter can be examined within a single blood sample. Applying artificial intelligence and machine learning will help determine which tests will help and which are unnecessary. In the meantime, clinical labs can employ simple approaches to decrease the amount of blood patients lose to diagnostic tests, lowering their risk of developing HAA, and improving their overall outcomes.