Packaging optimization through transport simulation
Pneumatic tube systems can shorten transportation times for blood samples. A new Danish pneumatic tube system (TEMPUS600®) transports samples at 10 m/s. The system requires no packing or unpacking of the samples. It makes it possible to send the samples directly to the bulk loader of an automated laboratory line.
The quality of samples can be affected during transportation. This can lead to pre-analytical errors, e.g. hemolysis and a subsequent increase in the concentration of some analytes such as potassium. Transport conditions can be characterized using mini data loggers that measure temperature, humidity, pressure and acceleration [1]. We have investigated the influence of the TEMPUS600® pneumatic tube system on sample quality.
Methods
Duplicate blood samples were taken from 20 volunteers. One set of samples was transported by courier, the other by pneumatic tube system (TEMPUS600®; TIMEDICO A/S; Bording, Denmark). During transportation, temperature and acceleration were continuously measured by a mini data logger (Fig. 2) (MSR145®; CiK Solutions GmbH; Karlsruhe, Germany). After transport, clinical chemistry, hematology and coagulation parameters were measured and compared, and the corresponding g-forces were calculated.
Fig. 1a
Fig. 1b
Fig. 1c
Results and discussion
Although the samples were accelerated to up to 18 x g (pneumatic tube system) or 6 x g (courier) during transportation (Fig. 3), there were no relevant differences between conventional pneumatic tube systems and the "single sample" pneumatic tube system with regard to the cumulative g-forces (vector sum [1]). The medians of the results differed by less than 10% for all analytes investigated (Table 1). The mean relative differences of the medians were 8.1% for LDH (lactate dehydrogenase) and 6.3% for free Hb (hemoglobin). Both analytes showed lower values during pneumatic tube transport. There were no differences between the mean relative differences for the potassium concentration.
Fig. 2
Fig. 3
Tab. 1 - Comparison of medians and mean relative differences depending on the mode of transportation
| Median Courier |
Median Pneumatic tube |
Mean relative difference difference [%] |
|
|---|---|---|---|
| LDH [μcatal/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 [mmol/l] | 0.39 | 0.39 | 0.0 |
| Thrombocytes [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 |
| Quick [%] | 108.0 | 109.5 | - 1.4 |
| aPTT [s] | 27.0 | 27.0 | 0.0 |
Conclusion
The use of a "single sample" pneumatic tube system significantly reduces the transportation times of samples. The acceleration forces acting on the samples during transportation do not influence the analysis results. The relative differences between the results are within the order of magnitude of the measurement inaccuracies of the assays used. The entire workflow is considerably improved by the reduction in processing times on the station and in the laboratory, without affecting the sample quality.
Literature
[1] Streichert T, Otto B, Schnabel C, Nordholt G, Haddad M, Maric M etal. Determination of Hemolysis Thresholds by the Use of Data Loggers in Pneumatic Tube Systems. Clinical Chemistry 2011; 57(10):1390-7