PT  - JOURNAL ARTICLE
AU  - Austin, Melissa
AU  - Ferrell, Chris
AU  - Reyes, Morayma
TI  - Do Elevated Hematocrits Prolong the PT/aPTT?
AID  - 10.29074/ascls.26.2.89
DP  - 2013 Apr 01
TA  - American Society for Clinical Laboratory Science
PG  - 89--94
VI  - 26
IP  - 2
4099  - http://hwmaint.clsjournal.ascls.org/content/26/2/89.short
4100  - http://hwmaint.clsjournal.ascls.org/content/26/2/89.full
SO  - Clin Lab Sci2013 Apr 01; 26
AB  - The Clinical and Laboratory Standards Institute guidelines require special processing of whole blood specimens with hematocrits greater than 55% due to the possibility of spurious prolongation of routine coagulation studies (PT, aPTT). As samples with hematocrits above 60% are rare at our institution, our study seeks to determine the effect of relative citrate excess on routine coagulation studies in samples with hematocrits of 60% to determine whether special processing is necessary. A calculated volume of 3.2% citrate was added to 1 mL aliquots of 40 whole blood samples in citrated tubes from adult patients to simulate a hematocrit of 60%. A dilutional control was created by adding an equivalent volume of saline to a separate 1 mL aliquot. Routine coagulation studies (PT, aPTT) were run on both samples on the STA Compact Analyzer in accordance with manufacturer instructions. While a paired Student's t-test demonstrated a clinically significant change in both PT and aPTT with the addition of citrate (p = 0.0002 for PT and p = 0.0234 for aPTT), clinical management would not have been altered by any observed change. More interestingly, we observed a shortening of 27/40 PTs and 23/40 aPTTs rather than the expected prolongation. Based on our data, no adjustment of citrate volume appears to be necessary in samples with hematocrits less than or equal to 60%.ABBREVIATIONS: CLSI - Clinical and Laboratory Standards Institute, PT - prothrombin time, aPTT - activated partial thromboplastin time, CBC - Complete Blood Count