Evaluation of a fast single sample pneumatic tube system

 
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A study of transport from blood samples in pneumatic tube systems by University Medicine Greifswald (D).

Authors: Juliane Suchsland, Anne Greiser, Thomas Streichert, Benjamin Otto, Stefan Bollmann, Matthias Nauck, Astrid Petersmann

Background

Pneumatic tube systems (PTS) can reduce transport time of blood samples. A new Danish PTS (TEMPUS600®) which does not require packing and unpacking of samples, transports samples with 10 m/s. It allows sending of samples directly into the bulk loader of a laboratory automation system. The quality of samples can be influenced during transport and may result in preanalytical errors like hemolysis and increase of analyte concentrations such as potassium. With mini data loggers, which measure temperature, humidity, pressure and acceleration, transport conditions can be described [1]. We investigated influences of TEMPUS600® on the quality of samples.

Methods

Duplicate blood samples of 20 volunteers were drawn. One set of samples was transported by courier and the other by PTS (TEMPUS600®; TIMEDICO A/S; Bording, Denmark). During transport, a mini data logger MSR145 (Fig. 2) (CiK Solutions GmbH; Karlsruhe, Germany) continuously measured temperature and accelerations. After transport clinical chemistry, hematology and coagulation parameters were measured, compared and the corresponding g-forces were calculated.

Fig. 1a: Tempus600® station on the ward. Source: University Medicine Greifswald
Fig. 1a
Fig. 1b: Rack with samples. Source: University Medicine Greifswald
Fig. 1b
Fig. 1c: PTS ending in the bulk loader of the laboratory automation system. Source: University Medicine Greifswald
Fig. 1c

Results and Discussion

Though samples in PTS were subject to maximum accelerations of ~18 g compared to ~6 g of courier transport (Fig. 3), the cumulated forces (vector sum; [1]) did not reveal relevant differences between the conventional and single sample PTS. Medians of results differed less than 10% for all investigated analytes (Tab. 1). Mean relative differences of medians for LDH (lactate dehydrogenase) and free Hb (hemoglobin) were 8.1% and 6.3% respectively, both showing lower values in PTS samples. There was no difference between mean relative differences for potassium.

Fig. 2: Data logger MSR145, waterproof silicon tube with 260 mAh battery.
Fig. 2
Fig. 3: G–forces acting on samples during transport by courier (left) and by PTS (right); black, green and purple lines represent g-forces in x-, y– and z–direction, respectively; red line represents temperature in °C. Source: University Medicine Greifswald
Fig. 3

Tab. 1 – Comparison of medians and mean relative difference depending on transport type

  median
courier		 median
PTS		 mean relative
difference [%]
LDH [μkatal/l] 3.04 2.79 8.1
free hemoglobin [μmol/l] 16 15 6.3
potassium [mmol/l] 3.9 3.9 0.0
sodium [mmol/l] 138.0 138.0 0.0
creatinine [μmol/l] 71.0 69.0 2.8
glucose [mmol/l] 5.4 5.1 5.6
hemoglobin [mmol/l] 7.9 7.8 1.3
hematocrit 0.39 0.39 0.0
platelets [Gpt/l] 244.5 244.0 0.2
erythrocytes [Tpt/l] 4.20 4.25 – 1.2
leukocytes [Gpt/l] 5.87 5.75 2.0
thromboplastin time [%] 108.0 109.5 – 1.4
aPTT [s] 27.0 27.0 0.0

Conclusion

Using a single sample PTS noticeably decreases transport time of samples. Acceleration forces acting on samples during transport do not impact the analytical results in a clinical relevant way. Relative differences between results are within the magnitude of the imprecision of the utilized assays. The overall workflow is improved considerably by decreasing hands on time on the ward and in the laboratory without impacting sample quality.

Literature

[1] Streichert T, Otto B, Schnabel C, Nordholt G, Haddad M, Maric M et al. Determination of Hemolysis Thresholds by the Use of Data Loggers in Pneumatic Tube Systems. Clinical Chemistry 2011; 57(10):1390–7

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