Testing the Testing Tool: ISTH Bleeding Assessment Accurately Predicts Patients With Platelet Function Disorders

In patients with suspected platelet function disorders, the International Society on Thrombosis and Hemostasis bleeding assessment tool (ISTH-BAT) proved to be a useful instrument for identifying patients with these disorders, a new study published in the Journal of Thrombosis and Haemostasis suggested.

“Our findings support the implementation [of this tool] in the work-up of patients with a suspected bleeding disorder,” study author Michael Nagler, MD, PhD, of the University Hospital Inselspital in Bern, Switzerland, told ASH Clinical News. “A positive scoring in the absence of coagulation disorders might trigger testing of platelet function, while it can be withheld in patients with a negative scoring.” He added that the tool might save both time and money because it can be applied in any setting, without a specialized laboratory.

The ISTH-BAT covers 14 sites of bleeding to record both the presence and the severity of bleeding symptoms, the study authors explained. While it has been validated in patients with von Willebrand disease (VWD), its diagnostic utility for platelet function disorders has not been established.

In this analysis, researchers assessed the diagnostic value of the ISTH-BAT in 555 patients who were referred to a specialized outpatient clinic in a tertiary university hospital in Switzerland for a suspected bleeding disorder between January 2012 and March 2017. Approximately two-thirds of patients (66.9%) were female, and the median age was 43.7 years (range = 29.3-61.7).

Before consultation, patients completed a 13-item questionnaire that evaluated the presence and severity of bleeding associated with the following:

  • skin, nose, oral cavity, gastrointestinal and urogenital systems, joints and muscles
  • minor injuries, dental procedures, surgery, transfusion requirements
  • ingestion of drugs known to affect hemostasis
  • family history

During the consultation, physicians took a detailed medical history and applied the ISTH-BAT prior to laboratory testing, and the scores were challenged by another experienced attending physician. Patients were instructed to stop anticoagulant therapy, antiaggregant treatment, nonsteroidal antirheumatic drugs, and/or selective serotonin reuptake inhibitors 10 days prior to consultation.

Blood samples were collected for standard coagulation and platelet function testing, including testing blood count and mean platelet volume, prothrombin time, and coagulation factor levels. If these initial platelet function test results came back within normal ranges, secondary tests using light transmission aggregometry and platelet flow cytometry were performed.

“A positive scoring in the absence of coagulation disorders might trigger testing of platelet function, while it can be withheld in patients with a negative scoring.”

—Michael Nagler, MD, PhD

Of the 555 patients who underwent this protocol, 288 patients (51.9%) were diagnosed with a bleeding disorder, comprising the following underlying types:

  • possible platelet function disorder (11.5%)
  • confirmed platelet function disorder (9.7%)
  • VWD (9.1%)
  • mild hemophilia (0.9%)
  • deficiency of other coagulation factors (1.3%)
  • fibrinogen disorders (1.1%)
  • disorders of fibrinolysis (1.3%)
  • anticoagulant treatment (0.9%)
  • systemic disorders (6.9%)

Of the 118 patients with a possible platelet function disorder, 54 (46%) had a confirmed diagnosis. In contrast, diagnostic evaluation was inconclusive in 64 patients (54%).
When reviewing the ISTH-BAT scores of patients with and without bleeding disorders, the researchers found that higher ISTH-BAT scores were associated with bleeding disorders. The median ISTH-BAT score of those without a diagnosis was 2 (range = 1-4), while the median score in those with a possible platelet function disorder was 4 (range = 3-7). In addition, patients with a confirmed platelet function disorder had a median ISTH-BAT score of 7 (range = 5-9).

“The predictive value of ISTH‐BAT for the presence of platelet function disorders was good,” the authors reported, with high sensitivity and specificity. In men, the test’s sensitivity was 76.9% and specificity was 62.4% at a score threshold of 4; for women, the sensitivity and specificity were 52.1% and 86.1%, respectively, at a threshold score of 6.

The study authors wrote that the ISTH-BAT might be useful for “triggering a referral of patients with any bleeding tendency at all,” such as patients with platelet function disorders and VWD. The screening tool also could be used to trigger studies of platelet function in patients with normal initial blood test results.

A limitation of the study included the high proportion of patients with suspected platelet function disorders rather than confirmed disorders, primarily due to the inappropriate completion of several diagnostic evaluations. The researchers added that the ISTH-BAT may not be helpful for differentiating between types of mild bleeding disorders, such as platelet function disorders from VWD, nor do they suggest the tool can replace platelet function studies.

The authors report no relevant conflicts of interest.

Reference

Adler M, Kaufmann J, Alberio L, Nagler M. Diagnostic utility of the ISTH bleeding assessment tool in patients with suspected platelet function disorders. J Thromb Haemost. 2019;17:1104-1112.