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More on PTT Specimen Storage Time

On November 1 I replied to a question from Joe Lamb, Columbus, GA about room temperature storage of specimens for partial thromboplastin time (PTT) assays that are sent to reference laboratories. Joe was concerned that his reference lab claimed PTT results were valid on specimens less than 24 hours old, whereas the CLSI Guideline H21-A5 sets the limit at four hours. In follow-up, H21-A5 permits for room-temperature whole-blood storage beyond four hours provided the local institution provides in-house data. This qualifying statement is based upon O’Neill EM, Rowley J, Hansson-Wicher M, et al. Effect on 24-hour whole-blood storage on plasma clotting factors. Transfusion 1999;39:488–91. This reference provides the justification Joe is looking for. Geo.

Comments (1)
Anticoagulant Therapy
Mar 10, 2012 4:45pm

Validity of the APTT and storage time somewhat depends on th
Validity of the APTT and storage time somewhat depends on the intended use. For APTT testing related to monitoring of unfractionated heparin, the CLSI Guideline H21-A5 actually sets the limit at 1hr. For other intended uses the guideline limit is 4 hrs, but several publications indicate that stability may be as high as 24 hrs. The issue of storage, and sample processing and transport, for hemostasis testing is extensively detailed in the following publication (soon to be published!):

Adcock-Funk DM, Lippi G, Favaloro EJ. Quality standards for sample processing, transportation and storage in hemostasis testing. Semin Thromb Hemost; 2012: in press.

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