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| Prothrombin Time, Activated Partial Thromboplastin Time and Low Molecular Weight Heparin Testing Practices in a Survey of 800 Randomly Selected U.S. Hospitals |
| Topic:
Hematology/Coagulation |
| S. Shahangian, A. K. Stankovic, I. M. Lubin, J. H. Handsfield, M. D. White. , CDC, Atlanta, GA, |
| Presentation Number: A-8 |
| Keyword:
Coagulation laboratory practices, U.S. hospitals, Quality assurance and quality improvement |
Context: Coagulopathy and bleeding disorders are major public health concerns, and coagulation laboratory tests constitute a principal component of clinical management.
Objective: To assess variability of hospital coagulation laboratory practices in testing for prothrombin time (PT), activated partial thromboplastin time (aPTT) and low molecular weight heparin (LMWH).
Methods: A group of coagulation laboratory experts and survey methodologists assisted in the design of this 2001 survey of 800 randomly-selected hospital coagulation laboratory directors (response rate, 79%; sampling rate, 14%), and further evaluated the content and format of the survey before pilot testing it in 9 hospital coagulation laboratories. Sampling frame was hospitals listed in the 1999 directory of the American Hospital Association, known to include 95% of all hospitals in the U.S. Participants had the option of responding via Internet, and 20 (3%) did so. Inconsistent responses were excluded from data analysis.
Results: Of the 629 responding, 612 (97%) stated that they performed coagulation testing.
Assaying PT. Of the 605 valid responses, all noted performing PT assay. Almost all (99.8%) reported PT results as international normalized ratio (INR); 97% reported results in seconds and/or as therapeutic PT ratio. Three percent reported PT results as INR only. Of the 585 respondents, 437 (73%) used 109 mmol/L (3.2%) sodium citrate as anticoagulant, and 8 (1%) used both 109 mmol/L and 129 mmol/L (3.8%) sodium citrate. Of the 576 valid responses, 531 respondents (92%) reported they conducted in-house evaluations to establish reference intervals for their PT assay. Of the 601 valid responses, 100 respondents (17%) reported determining sensitivity of their PT assay to heparin. Of the 540 valid responses, 271 respondents (50%) reported selecting PT-thromboplastin reagents insensitive to heparin in the heparin therapeutic range. International sensitivity index of current thromboplastin lots used by the respondents was 0.89—2.63 (average, 1.60; median, 1.81; n = 567).
Assaying aPTT. Of the 608 respondents, 601 (99%) reported performing aPTT assay. Of the 559 valid responses, 355 respondents (64%) reported they had an aPTT therapeutic range for heparin when monitoring heparin therapy. Of the 357 respondents, the following proportions reconfirmed the aPTT therapeutic range: 79% when new instrumentation was used, 75% when new reagent lots were used, 51% when new reagents were used, and 47% when new instrumentation, new reagent lots or new reagents were used (47%). Of the 557 respondents, 535 (96%) assayed specimens for aPTT within 4 h after phlebotomy. Of the 533 respondents, 467 (88%) centrifuged specimens within 1 h of collection. Specimens were kept at room temperature by 419 of 511 (82%) and at 4 °C by 101 of 455 (22%) respondents before aPTT testing.
Monitoring LMWH. Of the 579 valid responses, 82 respondents (14%) reported monitoring LMWH therapy. Forty-seven of the 65 respondents (72%) used aPTT assay to monitor LMWH therapy, while 35 of the 66 respondents (53%) used an anti-Xa assay to do so.
Conclusion: There is substantial variability in certain coagulation laboratory practices. Some of these practices are not consistent with current guidelines, and they may impact patient outcome. |
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