Abstract Number: PB0684
Meeting: ISTH 2020 Congress
Background: A diagnostic algorithm for reflex coagulation investigations (CI) with factor testing for prolonged lupus insensitive activated partial thromboplastin time (aPTT) is routinely done at London Health Science Center (LHSC), Ontario.
Aims: We aim to determine the clinical utility of the CI diagnostic algorithm.
Methods: We retrospectively reviewed all potential CI [lupus insensitive aPTT of ≥ 32s (normal range 20s-29s)] from April 2014 to June 2019 in our institution. The diagnostic algorithm requires completion of CI only if deemed clinically necessary by the hemostasis technician via chart review to ensure no interfering medications and meets the predetermined clinical criteria (preoperative sample or unexplained bleeding). If the criteria for CI are met, we complete a one-stage factor assay activity for Factor VIII(FVIII), IX(FIX) and XI(FXI). Data were obtained through the electronic medical records to capture clinical characteristics, laboratory findings, prophylactic hemostatic replacement and bleeding outcomes.
Results: 3317 samples from 2940 patients were identified as potential CI during the study period. 263 distinct patients met the criteria for CI and had factor assays completed. Of those, 55 (21%) patients had abnormal factor testing with potential clinical implications (Table 1). Most had single factor deficiency (95%) with FXI deficiency as the most common deficiency (73%). Only 9 patients received formal consultation with hematology, and 14 patients had confirmation of etiology for factor deficiency on subsequent testing (Table 1). Table 2 lists the type of surgery including bleeding outcomes. Only 1 patient received prophylactic hemostatic therapy.
Conclusions: Reflex coagulation factor testing is unique to our institution at LHSC. Through the application of a diagnostic screening algorithm, we were able to identify rare bleeding disorders such as acquired hemophilia earlier through screening aPTT alone. The low follow up rates for further testing of an identified factor deficiency suggests potential lab alert fatigue from ordering physicians.
| Characteristics | N; (range) |
| FVIII deficiency | 7; (4% – 48% FVIII activity) |
| FIX deficiency | 2; (6% – 49% FIX activity) |
| FXI deficiency | 42; (4.5% – 65% FXI activity) |
| Diagnosed Etiology for factor deficiency | N; (notes) |
| Congenital FXI deficiency | 3; (1 severe, 2 partial deficiency) |
| Congenital mild FVIII deficiency | 3 |
| Congenital mild FIX deficiency | 1 |
| Factor inhibitor | 1 FVIII inhibitor (8 BU), 1 FIX inhibitor (6.4 BU) |
| other | 5 |
[Table 1. Review of 55 patients with abnormal CI]
| Surgical Bleed Risk | No. of patients based on Factor Deficency | Range of Factor Activity Level | Post-op bleeding, N | Comments | |
| Major risk | FVIII | 3 | 25-48% | 0 | Temporal lobe lobectomy; total knee replacement; major urologic procedure – no hemostatic prophylaxis |
| FIX | 0 | – | – | ||
| FXI | 23 | 29-65% | 2 | Combination of major abdominal and urologic procedure in patient with FXI of 29% – no bleeding; Factor activity in bleeding patient: 38%, 62% | |
| Moderate risk | FVIII | 0 | – | – | |
| FIX | 0 | – | – | ||
| FXI | 7 | 9-63% | 1 | FXI 7 9-63% 1 Factor activity in bleeding patient: 27%; Colonoscopy with biopsy in patient with FXI of 9% – no bleeding | |
| Low risk | FVIII | 3 | 27-42% | 2 | Factor activity in bleeding patient: 27%, 42% |
| FIX | 0 | – | – | ||
| FXI | 2 | 43-46% | 0 | ||
[Table 2. Types of surgical procedures in patients with abnormal CI including bleeding complications]
To cite this abstract in AMA style:
Mansory EM, Bahodi F, Phua CW. Institutional Review of Reflex Factor Coagulation Testing in Patients with an Unexplained Prolonged aPTT [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/institutional-review-of-reflex-factor-coagulation-testing-in-patients-with-an-unexplained-prolonged-aptt/. Accessed September 24, 2023.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/institutional-review-of-reflex-factor-coagulation-testing-in-patients-with-an-unexplained-prolonged-aptt/