Clinica Chimica Acta

2 Letter to the editor
Table 1
Effects of tourniquet application vs. transilluminator device in blood sample collection on coagulation parameters.
G1 (N=50)
G2 (N=50)
Desirable
bias (%)
Mean value±SD
of transilluminator
Mean value±SD
of 30 s tourniquet
p-Value Mean %
difference
Mean value±SD
of transilluminator
Mean value±SD
of 90 s tourniquet
p-Value Mean %
difference
FIB (mg/dl) 4.8 384.9±94.9
[240.0–604.8]
PT (s) 2.0 12.32±3.20
[10.30–14.21]
APTT (s) 2.3 29.86±4.28
[22.50–33.80]
385.1±94.9
[240.0–605.0]
12.30±3.23
[10.31–14.19]
29.80±4.30
[22.50–33.77]
N0.05 0.05 358±72
[190–512]
N0.05 −0.2 14.47±7.94
[10.9–38.9]
N0.05 −0.2 31.80±7.90
[25.8–36.7]
364±72
[199–525]
14.41 ±8.00
[10.8–37.4]
31.70 ±7.80
[25.3–35.1]
0.002 1.7 ⁎
N0.05 −0.4
N0.05 −0.3
Desirable
bias (%)
G3 (N=50)
Mean value±SD
of transilluminator
FIB (mg/dl) 4.8 288±89
[173–540]
PT (s) 2.0 12.89±1.61
[11.0–18.4]
APTT (s) 2.3 31.70±4.50
[24.1–44.3]
Mean value±SD
of 120 s tourniquet
296±93
[189–545]
12.67±1.57
[10.9–18.0]
31.20±4.40
[20.1–38.7]
p-Value Mean %
difference
G4 (N=50)
Mean value±SD
of transilluminator
0.001 3.0 ⁎⁎ 361±85
[218–495]
0.003 −1.7 ⁎⁎ 12.65±3.29
[11.0–15.1]
0.009 −1.5 ⁎⁎ 30.20±4.40
[22.5–42.3]
Mean value±SD
of 180 s tourniquet
385±95
[240–605]
12.30 ±3.23
[8.7–14.2]
29.80 ±4.30
[22.5–22.8]
p-Value Mean %
difference
0.001 6.7 ⁎⁎
0.001 −2.8 ⁎⁎
0.002 −1.4 ⁎⁎
The values were mean ±SD [range: minimum–maximum]. The bold p-values are statistically significant (pb0.05) and bold mean % differences represent clinically significant
variations, when compared with desirable bias [38].
⁎ pb0.05 vs. G1.
⁎⁎ pb0.05 vs. G1 and G2.
The results of this investigation are shown in Table 1. InG1no
significant increases were observed in coagulation parameters
evaluated after 30 s of the tourniquet application. In G2, after 90 s of
the tourniquet application, a significant increase was observed in
fibrinogen. In G3, significant increases in FIB, PT and APTT were
observed after 120 s of the tourniquet application. In G4 significant
increases were observed in all coagulation tests evaluated after 180 s
of the tourniquet application. However, a clinically significant variation,
as compared with the current desirable quality specifications
[38], was only observed for fibrinogen and PT after 3 min of stasis
(G4).
Our results demonstrate that the prolonged stasis consequent on
tourniquet application for 120 s causes significant reduction of PT and
APTT values in both tests (Table 1), a well known phenomenon of in
vitro activation, thus paving the way for possible errors in critical
patient management and follow-up. As reported, rarely the expert
phlebotomist concludes the collection of diagnostic blood specimens
within 60 s of tourniquet application [18]. Several concurrent causes
might contribute to lengthen the tourniquet time even over 3 min,
such as a difficult location of an appropriate venous access, selection
of the most suited blood collection system, needle insertion into the
vein, collection of many tubes, etc. [3,5,6,9,15–17]. As regards
fibrinogen, the significant increase observed in groups G2, G3, and
G4 appears on overall modest and could be considered not clinically
significant. Nevertheless, even modest increases of fibrinogen, a
marker of inflammation, have been associated with future coronary
heart disease and with unstable and stable coronary artery disease
and coronary complications after interventions [39]. Thus the use of
tourniquet could generate false positives and prospectively induce the
caring physicians to adopt undue treatments. On the contrary,
transillumination devices appear able to eliminate such risk [40]. In
order to deal with some of the above issues, the quality laboratory
manager might devise and adopt improved blood collection procedures
with no or very reduced tourniquet times, e.g., by implementing
transillumination devices after accurate re-evaluation of the
whole blood collection procedures employed by phlebotomist [7].
Obviously such a process of change of blood collection procedures
should be supported by adequate practical instructions provided by
expert professionals. In conclusion, the results we obtained demonstrate
that by employing the recommended procedure of tourniquet
application with gold standard time (30 s) [10–12] in blood collection,
the performance of the coagulation routine testing is identical to that
shown by blood collected with the aid of transillumination. Probably
the errors induced by venous stasis on specialized coagulation tests
like D-dimer, Factors VII, VIII and XII [17] would be eliminated too
using the transillumination. Further insight has to be made in this
respect. Moreover, the whole results demonstrate that transillumination
devices can eliminate the venous stasis and improve the
quality process in preanalytical phase especially in phlebotomy
procedures, mostly when considering that inappropriately prolonged
tourniquet application is rather widespread and no common rules
and/or guidelines appear applied in this respect. These results do
apply to our experimental design, even though they represent a viable
basis for the governance of the preanalytical variability related to
sample stasis.
No potential conflicts of interest relevant to this article were
reported.
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Please cite this article as: Lima-Oliveira G, et al, Elimination of the venous stasis error for routine coagulation testing by transillumination,
Clin Chim Acta (2011), doi:10.1016/j.cca.2011.04.008