From Anita Elledge, MT (ASCP), blood bank/coagulation supervisor, Sierra Vista Regional Health Center, AZ: Our coagulation testing is done on a Stago Compact instrument. The linear range is 20–200 s for the activated partial thromboplastin time (APTT, PTT). We have a policy that any PTT result <22 s must be redrawn, not just rerun the same sample, because it is said that a low PTT result should not occur and is almost always due to a bad collection. I can’t seem to find any documentation that confirms the < 22 s result being a point for this “recollect.” Can you give me a resource for information or any further help with this?
Hello, Ms. Elledge, and thank you for your question. I posted a similar question, named “Shortened PTT” on March 13, 2013, and attracted a number of responses. In my post I stated that “only technical artifacts shorten the PTT to less than the lower limit of the reference interval. Artifacts could include partial activation of the coagulation cascade through a specimen collection error, specimen chilling, excessive incubation with the initial PTT reagent prior to adding CaCl2 solution, incorrect reagent formulation, or wrong incubation temperature.” The comments I received provided references for a number of circumstances in which a shortened PTT may indicate a thrombotic condition.
Nothing in the March 13 post specifically answers your question, however, as there is not a study that indicates at what point there should be a redraw; however your local policy seems reasonable. Despite the helpful comments from Drs. Emmanuel Favaloro andVadim Kostousov, most shortened PTTs reflect a specimen artifact or preanalytical variable, and warrant a recollect. If the second specimen is again shortened, it may be an indication of increase thrombosis risk.
Short APTT is often associated with very high factor VIII le
Short APTT is often associated with very high factor VIII level. Check the factor VIII levels if a particular patient is consistently getting short APTTs with no evidence of haemolysis.
Based on this report, repeated blood sampling might not be t
Based on this report, repeated blood sampling might not be the appropriate strategy in case of overall short APTT. However, due to rare incidence of extremely shortened APTT less than 22 s, a local observational study might be useful in order to confirm or reject the utility of repeated blood sampling in order to eliminate preanalytical factors in this particular situation. Among 202 APTTs less than 26s, they have only 24 (12%) less 22 sec.
From the previous paper: “we have confirmed the short APTT o
From the previous paper: “we have confirmed the short APTT on repeated testing in samples of 30 consecutive patients obtained from repeated blood collection. The repeated APTT was determined within 5h after the initial blood collection. A repeated short APTT was detected in 28 patients. Only 2 patients showed APTTs less than 26s for the second blood sample. Both of these patients had APTTs of 25 s in the first collected blood sample.”
Unfortunalely, the size of comments is limited here, that’s
Unfortunalely, the size of comments is limited here, that’s why the idea of my comments is lost, try to split it for parts.
I would like to add some evidence, published by Edwin ten Bo
I would like to add some evidence, published by Edwin ten Boekel & Piet Bartels in their paper “Abnormally Short Activated Partial Thromboplastin Times Are Related to Elevated Plasma Levels of TAT, F1+2, D-Dimer and FVIII:C” published in Pathophysiol Haemost Thromb 2002;32:137142. They reported short APTTs as 26 s for the second blood sample. Both of these patients had APTTs of 25 sec in the first collected blood sample…”