Streamlined approach to testing for heparin-induced thrombocytopenia improves diagnostic accuracy

A new study appearing in The Journal of Applied Laboratory Medicine (JALM) has found that a simplified version of the standard screening method for identifying heparin-induced thrombocytopenia (HIT)—a dangerous side effect of the blood thinner heparin—did a better job than the full technique of identifying which patients had the condition.

The results provide striking evidence that systematic, data-driven approaches to health care can not only save time and money, but improve patient care. The study is featured in a special issue of JALM highlighting the value of diagnostic stewardship, a collaborative approach to enhancing clinical laboratory testing.

HIT is tricky to diagnose because thrombocytopenia (low blood platelets) can have various causes and is common in hospitalized patients. Only 1%–5% of patients who take heparin develop HIT, but those who do are at risk of life-threatening bleeding or heart attacks.

Doctors need to know which cases are directly linked to heparin so they can switch those patients to another blood thinner. That said, non-heparin anticoagulants are expensive and hard to monitor, so clinicians want to reserve them for the patients who need them for safety.

Adding to the complexity, two different lab tests are used to help identify HIT. ELISA (enzyme-linked immunosorbent assay) helps weed out people who don’t have HIT, while the serotonin release assay (SRA) serves as the gold standard for confirming it. However, since SRA is costly and offered only in specialized labs, clinicians often rely on a combination of ELISA results, patient symptoms, and other clinical clues to make the diagnosis.

In the study, researchers analyzed the lab results of 1,011 ELISA tests and 169 SRA tests performed between December 2016 and December 2021 on patients in the University of Iowa Health Care System. Specifically, they compared two approaches for interpreting ELISA results using optical density (OD) measures, which help gauge the presence of HIT-specific antibodies in a blood sample.

The first method, “percent inhibition,” requires clinicians to test samples in both high-heparin and low-heparin conditions in accordance with the manufacturer’s recommendations. The second method, “low-heparin OD,” requires only the low-heparin preparation. This approach is quicker, easier, and less resource-intensive than the first, which requires lab workers to inhibit heparin in the blood sample.

The authors found that the low-heparin OD method identified true cases of HIT (as confirmed by SRA) more accurately than the percent inhibition method among patients with positive or ambiguous ELISA test results.

With the more extensive technique showing no added value, the health system modified their ELISA reporting recommendations in 2023 to call for the sole use of the low-heparin OD approach. The researchers then compared patients’ HIT test results in a 5-month period before these changes were made with those in a 5-month period after the intervention.

They found that the intervention decreased the rate for ELISA positivity from 13% to 5% and reduced rates of SRA confirmatory testing overall, pointing to more efficient utilization of testing resources and a likely reduction in the unnecessary use of non-heparin anticoagulants. Moreover, during the pre-intervention period, 7 of 9 (78%) of positive or ambiguous ELISA tests had a corresponding confirmatory SRA order, compared with only 3 of 7 (43%) post-intervention.

“Elimination of the heparin-inhibition step significantly simplifies manual work for laboratorians performing the testing, saves reagent costs, and increases testing throughput,” wrote lead study author Dr. Meredith G. Parsons. “The removal of heparin inhibition also simplifies ELISA reporting and increases its utility for clinicians in guiding next steps in patient management.”

Provided by
Association for Diagnostic and Laboratory Medicine

A new study appearing in The Journal of Applied Laboratory Medicine (JALM) has found that a simplified version of the standard screening method for identifying heparin-induced thrombocytopenia (HIT)—a dangerous side effect of the blood thinner heparin—did a better job than the full technique of identifying which patients had the condition.

The results provide striking evidence that systematic, data-driven approaches to health care can not only save time and money, but improve patient care. The study is featured in a special issue of JALM highlighting the value of diagnostic stewardship, a collaborative approach to enhancing clinical laboratory testing.

HIT is tricky to diagnose because thrombocytopenia (low blood platelets) can have various causes and is common in hospitalized patients. Only 1%–5% of patients who take heparin develop HIT, but those who do are at risk of life-threatening bleeding or heart attacks.

Doctors need to know which cases are directly linked to heparin so they can switch those patients to another blood thinner. That said, non-heparin anticoagulants are expensive and hard to monitor, so clinicians want to reserve them for the patients who need them for safety.

Adding to the complexity, two different lab tests are used to help identify HIT. ELISA (enzyme-linked immunosorbent assay) helps weed out people who don’t have HIT, while the serotonin release assay (SRA) serves as the gold standard for confirming it. However, since SRA is costly and offered only in specialized labs, clinicians often rely on a combination of ELISA results, patient symptoms, and other clinical clues to make the diagnosis.

In the study, researchers analyzed the lab results of 1,011 ELISA tests and 169 SRA tests performed between December 2016 and December 2021 on patients in the University of Iowa Health Care System. Specifically, they compared two approaches for interpreting ELISA results using optical density (OD) measures, which help gauge the presence of HIT-specific antibodies in a blood sample.

The first method, “percent inhibition,” requires clinicians to test samples in both high-heparin and low-heparin conditions in accordance with the manufacturer’s recommendations. The second method, “low-heparin OD,” requires only the low-heparin preparation. This approach is quicker, easier, and less resource-intensive than the first, which requires lab workers to inhibit heparin in the blood sample.

The authors found that the low-heparin OD method identified true cases of HIT (as confirmed by SRA) more accurately than the percent inhibition method among patients with positive or ambiguous ELISA test results.

With the more extensive technique showing no added value, the health system modified their ELISA reporting recommendations in 2023 to call for the sole use of the low-heparin OD approach. The researchers then compared patients’ HIT test results in a 5-month period before these changes were made with those in a 5-month period after the intervention.

They found that the intervention decreased the rate for ELISA positivity from 13% to 5% and reduced rates of SRA confirmatory testing overall, pointing to more efficient utilization of testing resources and a likely reduction in the unnecessary use of non-heparin anticoagulants. Moreover, during the pre-intervention period, 7 of 9 (78%) of positive or ambiguous ELISA tests had a corresponding confirmatory SRA order, compared with only 3 of 7 (43%) post-intervention.

“Elimination of the heparin-inhibition step significantly simplifies manual work for laboratorians performing the testing, saves reagent costs, and increases testing throughput,” wrote lead study author Dr. Meredith G. Parsons. “The removal of heparin inhibition also simplifies ELISA reporting and increases its utility for clinicians in guiding next steps in patient management.”

Provided by
Association for Diagnostic and Laboratory Medicine