Let’s highlight Marianne Thawley’s question that appears in a comment on the March 8 post, Rapid INR Rise in Pneumonia, “What are some causes for decreased PTT results.” In my experience, only technical artifacts shorten the partial thromboplastin time (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. Elevated factor VIII, while it does not shorten the PTT, does render the PTT less sensitive to heparin, thus the assay may underestimate plasma heparin. Does anyone know of another circumstance, in particular, a physiological or pathological circumstance that shortens the PTT? Please add your comment below.
Mar 13 2013
Comments (6)Screening Assays
Hello Dr. Jasmina,
Hello Dr. Jasmina, Chilling the sample shortens the PTT time because it activates factor VII. Alana Smith MLT.
From George: in addition to Alana Smith’s comment, prolonged chilling may also cause high molecular weight von Willebrand factor multimers to precipitate from the plasma.
A short PPT was found in a
A short PPT was found in a patient with elevated factor VIII. Patients with mast cell activation disorder (MCAS or MCAD) can have elevated factor VIII. This factor also is an acute phase reactant. In this particular patient with lung pathology, I would consider both MCAS (elevated tryptase, urinary PGD2 may be elevated) plus acute phase reaction (increased factor VIII) as a possible cause of shortened PPT and possible hypercoagulability. MCAS commonly presents with shortness of breath, lung pathology, drop in blood pressure, and anaphylactic like presentation. Kounis syndrome can also occur in MCAS patients resulting in allergic trigger for coronary arteries to go into spasms resulting in coronary infarction. Other causes are listed in this interesting abstract: http://www.ncbi.nlm.nih.gov/pubmed/20614573.
Another source of short APTT is circulating phospholipids (P
Another source of short APTT is circulating phospholipids (PL) or PL microparticles:
…The aPTT was significantly shorter in ITP-S (p = 0.029). Interestingly, correlation analysis revealed that RMP, but not other C-MP, were associated with shortening of aPTT (p = 0.024) as well as with increased activities of factors VIII (p = 0.023), IX (p = 0.021) and XI (p = 0.0089)…
from Fontana V et al. Increased procoagulant cell-derived microparticles (C-MP) in splenectomized patients with ITP. Thromb Res. 2008;122(5):599-603.
…plasma microparticles provide coagulant material which shortens the activated partial thromboplastin time (APTT) and dilute simplastin time (DSTT) which is different from that contributed by commercial phospholipid preparations.
from Howard MA, et al. Coagulation activities of plasma microparticles. Thromb Res. 1988 Apr 1;50(1):145-56.
Greetings to all! I would like to add some comments: elevate
Greetings to all! I would like to add some comments: elevated FVIII indeed shortens APTT and the APTT falling below the lower reference range is depending on the initial APTT values and amount of rFVIII that is added to the specimen. For example, on order to decrease of APTT below 24.9 (our lower reference limit)FVIII should be increased up to 400% in plasma sample with initial APTT 28.2 s. Similar FVIII levels (300-400%) were noticed in patients with APTT < 24 s (Fig. 2) in "Edwin ten Boekel, Piet Bartels Abnormally Short Acivated Partial Thromboplastin Times Are Related to Elevated Plasma Levels of TAT, F1+2, D-Dimer and FVIII:C. Pathophysiol Haemost Thromb 2002;32:137142"
Hi all, shameless self-promotion: I would suggest the follow
Hi all, shameless self-promotion: I would suggest the following review: Lippi G, Salvagno GL, Ippolito L, Franchini M, Favaloro EJ. Shortened activated partial thromboplastin time: causes and management. Blood Coagul Fibrinolysis. 2010;21(5):459-63. Although most cases of shortened APTTs are due to preanalytical events (what George called ‘technical artifacts’), a proportion are due to in vivo events that may be associated with prothrombotic tendency.
Dear George,Thanks for the list of answers to this often enc
Dear George,Thanks for the list of answers to this often encountered lab result. Why does chilling the sample shorten the PTT?