Abstract
Context.—Technologic advances affecting analyzers used in clinical laboratories have changed the methods used to obtain many laboratory measurements, and many novel parameters are now available. The effects of specimen transport through a pneumatic tube system on laboratory results obtained with such modern instruments are unclear.
Objective.—To determine the effects of sample transport through a pneumatic tube system on routine and novel hematology and coagulation parameters obtained on state-of-the-art analyzers.
Design.—Paired blood samples from 33 healthy volunteers were either hand delivered to the clinical laboratory or transported through a pneumatic tube system.
Results.—No statistically significant differences were observed for routine complete blood cell count and white cell differential parameters or markers of platelet activation, such as the mean platelet component, or of red cell fragmentation. When 2 donors who reported aspirin intake were excluded from the analysis, there was a statistically, but not clinically, significant impact of transport through the pneumatic tube system on the mean platelet component. There were no statistically significant differences for prothrombin time, activated partial thromboplastin time, waveform slopes for prothrombin time or activated partial thromboplastin time, fibrinogen, or fibrin monomers.
Conclusions.—Although further study regarding the mean platelet component may be required, transport through a pneumatic tube system has no clinically significant effect on hematology and coagulation results obtained with certain modern instruments in blood samples from healthy volunteers.
Pneumatic tube systems (PTSs) allow rapid and cost-effective transport of patient specimens to clinical laboratories and are therefore widely used in modern medical centers. During transport in a PTS, samples are often subjected to high speeds (up to 25 feet or 7.6 m/s) and rapid acceleration and deceleration. These strong forces can potentially affect various laboratory parameters: changes in lactate dehydrogenase concentrations, decreases in antibody reactivity potentially affecting pretransfusion evaluations, and effects on blood gas measurements have been reported.1–6 Most recently, it has been shown that transportation of blood samples through a PTS may affect in vitro platelet function studies.7
The technology underlying automated hematology and coagulation analyzers used in routine clinical laboratories has progressed rapidly in the last 2 decades. Modern cell counters often combine a variety of methods, including colorimetry, flow cytometry, and selective cell lysis to provide well-established measurements such as complete blood counts (CBCs), white cell differentials, and reticulocyte enumerations, as well as many novel parameters including direct measurements of red cell fragmentation and platelet activation.8 Similarly, certain modern automated coagulation instruments can provide extremely sensitive indicators of activation of the clotting cascade, such as the concentration of fibrin monomers.9 The effects of specimen transport through a PTS on results obtained from such advanced systems have so far not been investigated. In this study, we report the effects of a state-of-the-art PTS on routine and novel hematology and coagulation laboratory results in blood samples obtained from healthy volunteers.
MATERIALS AND METHODS
Specimens
Paired blood samples from 33 healthy blood donors (18 female, 15 male) were collected by trained technologists into 2 Vacutainer K2EDTA Plus plastic tubes and into 2 Vacutainer Plus Citrate Tubes (BD Medical Systems, Franklin Lakes, NJ). The samples were obtained from a single venipuncture, and the order of the tubes (PTS vs hand carried) was alternated randomly. Paired samples were processed and analyzed at the same time.
Sample Transport
Two randomly selected samples from each donor (1 in a citrate tube and 1 in a K2EDTA tube) were sent via the PTS from a 22nd-floor inpatient ward to the clinical hematology laboratory. The other samples were hand carried to the laboratory. The laboratory is located on the second floor of a building adjacent to the clinical wards; the distance in the PTS between the 2 stations is approximately 1000 ft (305 m). Transport time in the tube system was approximately 2 minutes. The PTS used by our hospital is manufactured by Translogic (now Swisslog, Denver, Colo). The system functions at a constant speed of 25 ft/s (7.6 m/s) and uses transfer stations that accelerate and decelerate specimens during zone transfers.
Sample Analysis
Using the paired whole blood EDTA specimens, CBCs and white cell differentials were obtained on an ADVIA 2120 Hematology System (Bayer HealthCare Diagnostics Division, Tarrytown, NY) within 1 hour of venipuncture. This system uses a cyanide-free method for the measurement of hemoglobin, isovolumetric sphering and light scatter for all other red cell parameters, light scatter for platelets, and selective cell lysis, peroxidase staining, and light scatter for the white cell measurements.10 The CBC parameters included white blood cell counts, hematocrit, hemoglobin, red blood cell count, platelets, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and red cell distribution width. The white blood cell differential consisted of the percentages of neutrophils, lymphocytes, monocytes, eosinophils, basophils, and large unstained cells. In addition to the platelet count, the following platelet parameters were determined: platelet volume distribution width, which is a measure of platelet size variation; mean platelet component concentration (MPC), a measure of platelet granularity; the platelet component distribution width, a measure of the variation in platelet density; mean platelet mass; platelet mass distribution width; and the number of platelet clumps and of large platelets (>20 fL).11 The number of red cell fragments (<30 fL) was also enumerated. Erythrocyte sedimentation rates were determined on whole blood with a Ves-matic 20 analyzer (Élan Diagnostics, Smithfield, RI).
After centrifugation of the paired citrated specimens at 1500g for 10 minutes, coagulation assays were performed within 2 hours of collection or on samples frozen within 1 hour after venipuncture and stored at −70°C until assayed. Assays for prothrombin time (PT), activated partial thromboplastin time (PTT), and fibrinogen were performed on an MDA-180 analyzer using Simplastin L, Platelin L, and Fibriquik reagents (bioMerieux, Durham, NC). The MDA-180 detects clot formation by measuring changes in light transmittance. In addition to numeric values for coagulation assays, the instrument also provides graphs (called waveforms) of light transmittance over time during the formation of the clot in the sample cuvette. Furthermore, the MDA-180 provides a numeric value representing the slope of the initial part of the waveform, from the time reagents are added until clot formation occurs. These waveform tracings and slope values are useful for troubleshooting in the laboratory and for diagnosing disseminated intravascular coagulation. Fibrin monomers were measured on a STA-R analyzer using the Liatest FM reagent (Diagnostica Stago, Asnieres, France) using an immunoturbidimetric method.
Statistical Analysis
A 2-tailed paired t test was used to evaluate differences between hand-delivered samples and specimens sent through the PTS. Statistical analysis was performed using Microsoft Excel software (Microsoft, Redmond, Wash).
RESULTS
To determine the effects of transport through a PTS on results obtained from modern automated hematology and coagulation systems, we compared samples sent to the laboratory via PTS with hand-delivered samples drawn from the same donors at the same time. There were no statistically significant changes in CBC and white blood cell differential parameters between samples sent through the PTS and samples delivered by hand (Tables 1 and 2).
Complete Blood Count (CBC) Parameters in Paired Samples Delivered via Courier or by Pneumatic Tube System (PTS)*

White Cell Differential Parameters in Paired Samples Delivered via Courier or by Pneumatic Tube System (PTS)*

None of the platelet and red cell fragmentation parameters available on the ADVIA 2120 Hematology System were statistically significantly different between hand-delivered samples and specimens sent through the PTS (Table 3). The mean MPC, a measure of platelet activation, in samples transported by courier was 28.1 g/dL; in specimens transported by PTS, it was 28.2 g/dL (P = .07 for paired 2-tailed t test). Two of the donors indicated that they had taken aspirin shortly before the study. The specimens from these 2 volunteers showed a decrease by 0.5 g/dL in the MPC in the sample sent through the PTS in 1 donor and an increase by 0.2 g/dL in the other donor in the pneumatic tube sample. When analysis was repeated excluding these 2 aspirin specimens, the 2-tailed t test for paired samples yielded a P value of .04 (mean MPC 28.07 g/dL for hand-carried samples vs 28.2 g/dL for PTS samples). None of the other parameters reached statistical significance (P < .05) when the 2 aspirin samples were omitted. Mean platelet component concentration values were lower in samples transported via PTS in 10 donors, higher in 18 donors, and identical in both samples in 5 donors. The biggest difference in MPC was 0.7 g/dL (Figure 1).
Platelet and Red Cell Fragmentation Parameters in Paired Samples Delivered via Courier or by Pneumatic Tube System (PTS)*

Bland-Altman plot for mean platelet component concentration (MPC), a measure of platelet granularity and platelet activation, from paired specimens transported through a pneumatic tube system (PTS) or hand carried. Values on the x-axis indicate the average of the result from the PTS-transported tube and the result from the hand-carried tube. Figure 2. Bland-Altman plot for fibrin monomers from paired specimens transported through a pneumatic tube system (PTS) or hand carried. Values on the x-axis indicate the average of the result from the PTS-transported tube and the result from the hand-carried tube.
Bland-Altman plot for mean platelet component concentration (MPC), a measure of platelet granularity and platelet activation, from paired specimens transported through a pneumatic tube system (PTS) or hand carried. Values on the x-axis indicate the average of the result from the PTS-transported tube and the result from the hand-carried tube. Figure 2. Bland-Altman plot for fibrin monomers from paired specimens transported through a pneumatic tube system (PTS) or hand carried. Values on the x-axis indicate the average of the result from the PTS-transported tube and the result from the hand-carried tube.
No statistically significant differences between samples delivered by PTS versus hand-carried samples were observed for PT, PTT, or fibrinogen (Table 4). The PT and PTT waveforms were reviewed by an expert reader (E.V.C.) and no difference between hand-delivered samples and PTS samples was observed. The waveform slope values for PT and PTT were not influenced by transportation through the PTS (Table 4). Results of assays for fibrin monomers, an extremely sensitive marker of activation of the coagulation cascade, were also not influenced by transport through the PTS (Table 4 and Figure 2). Finally, there was no difference in the results of erythrocyte sedimentation rate assays in hand-delivered samples versus samples sent through the PTS (Table 4).
COMMENT
Effects of PTSs on laboratory results have been documented in the literature. Changes caused by a PTS include damage to erythrocytes, especially in underfilled blood draw tubes, with resulting release of lactate dehydrogenase and other markers of cell damage.1,3,12 Possible reductions in serum antibody activity by transport through a PTS have led to questions about the suitability of using a PTS for the transport of samples intended for compatibility testing in the blood bank.4 Interferences with blood gas measurements have also been reported.5,6
To the best of our knowledge, only 2 studies have investigated the effects of a PTS on hematology results.2,13 These articles, published in 1978 and 1992, used the Coulter S and the Coulter S+4 systems (Coulter Electronics, Inc, Hialeah, Fla), automated cell counters that have in most laboratories been replaced by newer models. Neither one of these investigations found an effect of the PTS on basic CBC parameters. Our investigation, using a state of the art analyzer, extends the validity of these data to the ADVIA 2120 system, a modern automated hematology system.
In addition to the standard CBC and white cell differential parameters, the ADVIA 2120 Hematology System also provides markers of red cell fragmentation and platelet activation.8 It is reassuring that these parameters were not affected by exposure to a PTS, suggesting that it is safe to send samples through a PTS prior to determination of these variables. Our finding of an almost statistically significant effect of the PTS on the MPC may be of interest and may indicate the need for further study. The MPC, or mean platelet component, is a measure of platelet granulation. Changes in the MPC have been shown to correlate with CD62 expression on the platelet membrane, electron microscopic changes associated with platelet activation, and various forms of in vitro platelet activation.11,14,15 The effects of exposure to the PTS did not reach statistical significance (P = .07 for all samples, P = .04 after exclusion of 2 donors who were on aspirin therapy) and the differences were minimal and unlikely to be of clinical significance. The report by Dyszkiewicz-Korpanty et al7 found an effect of PTS transport on platelet aggregation only in patients on aspirin.
Weaver et al2 compared PT and PTT results in paired hand-delivered samples with tubes sent through a PTS. They found no statistically significant difference for the PT between the 2 delivery methods. The mean PTT was statistically significantly shorter in the samples delivered via PTS (39.0 seconds vs 40.2 seconds; P < .05); however, the variance was not considered clinically significant, because it was within the standard deviation of the method used. Like our investigation, Steige and Jones16 found no effect of a PTS on fibrinogen levels. To the best of our knowledge, we are the first to investigate the effects of transport via PTS on fibrin monomers, an extremely sensitive marker of activation of the coagulation cascade, as well as PT and PTT waveform and slope values. PTT waveforms and corresponding slope values are a novel means of detecting disseminated intravascular coagulation,17 in which a slope that is more negative than that of the reference range is suggestive of disseminated intravascular coagulation and/or sepsis. In addition, clinical laboratories use the waveform tracings to troubleshoot abnormal results, for example, to determine if a PTT of more than 150 seconds needs to be repeated for confirmation or if the result can be reported. Again, the fact that transport through a PTS did not influence these results is reassuring.
An important limitation of our study is that most test results were in the normal range. Among the abnormal results, there was no clinically significant difference between samples transported through the PTS versus hand-delivered samples. The lack of significant differences in our study suggests that specimens intended for laboratory analysis of hematology and coagulation parameters can safely be transported with a PTS. Further studies involving specimens obtained from clinical samples (as opposed to the healthy donors used in our study) will be necessary to determine if our findings can safely be applied to patient populations.
Acknowledgments
We thank Mr Sean (Chun-Wai) Chan for expert secretarial assistance, Christopher Longchamps, BS, for providing details about the operations of the PTS, and all the members of the MGH Hematology Laboratory for sample analysis. We also thank Diagnostica Stago (Asniers, France) for providing the fibrin monomer assay reagents.
References
The authors have no relevant financial interest in the products or companies described in this article.
Author notes
Reprints: Alexander Kratz, MD, Department of Pathology, Columbia University College of Physicians and Surgeons, 622 West 168th St, PH3-303, New York, NY ([email protected])