From the Journals

Trial shows utility of small-volume blood collection tubes



A large Canadian clinical trial has found that using small-volume tubes to collect blood samples for laboratory testing of intensive care unit patients can reduce blood transfusions without affecting lab results.

“We showed in a large pragmatic cluster trial that automatically collect less blood for laboratory testing reduced red blood cell transfusions by about 10 units of red blood cells per 100 patients in the ICU,” lead study author Deborah M. Siegal, MD, associate professor at the University of Ottawa and scientist at the Ottawa Hospital Research Institute, said.

The study was coordinated by the Population Health Research Institute, an affiliate of McMaster University in Hamilton (Ont.) Health Sciences, where Dr. Siegal worked before moving to Ottawa.

Dr. Deborah M. Siegal

Dr. Deborah M. Siegal

The STRATUS randomized clinical trial, published in JAMA, involved 25 adult medical-surgical ICUs across Canada, where 21,201 patients were randomized to either standard-volume or small-volume tubes for collecting blood samples. During the course of the study, each site switched to the small-volume collection tubes.

“We also showed there were no negative effects on lab testing, and by that we measured the sufficiency of the specimens,” Dr. Siegal added. “We were able to show that there wasn’t a problem with the amount of blood that was available for the tests to be done.”

The samples were collected from February 2019 through January 2021, through the period of COVID-19 restrictions. Dr. Siegal explained that 6,210 patients admitted early in the COVID-19 pandemic were excluded from the primary analysis, but were included in secondary analyses.

Study results

While the study found no significant difference in RBC units per patient per ICU stage – a relative risk of .91 (95% confidence interval, 0.79-1.05; P = .19), it did find an absolute reduction of 7.24 RBC units/100 patients per ICU stay.

Findings from the secondary analyses, which included 27,411 patients, were:

  • A 12% reduction in RBC units per patient per ICU stay after switching from standard-volume to small-volume tubes (RR, 0.88; 95% CI, 0.77-1; P = .04).
  • An absolute reduction of 9.84 RBC units/100 patients per ICU stay (95% CI, 0.24-20.76).

In the primary analysis population, the median transfusion-adjusted hemoglobin was not statistically different between the standard- and small-volume collection tube groups, with an average difference of 0.1 g/dL (95% CI, –0.04 to .23), but it was lower in the secondary population, with a mean difference of .17 g/dL (95% CI, 0.05-0.29).

“Those patients that we analyzed in the secondary analysis population received about 36,000 units of blood, just in 25 ICU units in Canada in less than 2 years,” Dr. Siegal said. “If we saved 10 units per 100 patients, that’s 1,500 units of blood. That really speaks to a small effect at the individual patient level but really potential for widespread effect. We are now in a period of blood product shortage not only in Canada but worldwide.”

First clinical trial for small tubes

Dr. Siegal noted this was the first clinical trial to compare standard- and small-volume blood collection tools, “and also to show there is both a benefit and a lack of harm,” Dr. Siegal said. “We thought that a randomized trial was the best way to move the needle. If we could design a trial of a large population of patients to show benefit and no harm, it would be a win, and that’s in fact what happened.”

She added, “The tubes essentially have the same cost, work the same, and go on the same equipment the same way the standard-volume tubes do, so it wasn’t a practice change for people in the hospital.”

The study also found an identical low rate of unusable specimens did not differ regardless of the type of collection tube: less than .03%.

Dr. Siegal said the study group is collaborating with hematology stakeholders in Canada, including Canadian Blood Services, which provides blood plasma to the country’s provincial and territorial health systems, and is reaching out to the American Society of Hematology.

“We’re going to target both hematologists and critical care providers and, even more broadly than the critical care community, hospitals, because anemia is big problem in hospitals,” Dr. Siegal said. “I think we can think about this more broadly.”

The study received funding from the Hamilton Academic Health Sciences Organization. Dr. Siegal disclosed relationships with Bristol-Myers Squibb-Pfizer, AstraZeneca and Roche.

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