Influence of pneumatic tube delivery system on laboratory results

INTRODUCTION

The pneumatic tube system (PTS) is an automated and fast modality of transportation of biological samples, but it has been reported to induce preanalytical errors.

AIM

To study the influence of transportation by PTS on biochemistry tests which are particularly sensitive to haemolysis and atmospheric pressure variation.

MATERIALS AND METHODS

We compared laboratory results of arterial blood gas, sodium, potassium, chloride, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, glucose and haemolysis index of samples conveyed simultaneously by PTS and by courier.

RESULTS

We recruited 30 patients from the sampling room and 40 patients from the intensive care unit. Transport through PTS resulted in a significant increase in aspartate aminotransferase and potassium without exceeding the limits of acceptability. Potassium was significantly more increased for samples transported in a higher speed line (p = .048) but without exceeding the limits of acceptability. No significant impact was noted on haemolysis indices. The pO2 variations due to PTS transportation exceeded the limit of acceptability with significant intra-individual variations.

CONCLUSION

Our PTS is validated for biochemistry tests results. It reduces turnaround times without affecting sample quality. However, the interpretation of arterial blood gas results should be careful for samples transported by PTS.

Detection of preanalytical errors in arterial blood gas analysis

Introduction

Blood gas analysis (BGA) is an essential test used for years to provide vital information in critically ill patients. However, the instability of the blood gases is a problem. We aimed to evaluate time and temperature effects on blood gas stability.

Materials and methods

Arterial blood was collected from 20 patients into syringes. Following BGA for baseline, syringes were divided into groups to stand at 4°C and 22°C for 30, 60, 90, 120 minutes. All were tested for pH, partial pressure of carbon dioxide (pCO₂), partial pressure of oxygen (pO₂), oxygen saturation (sO₂), oxyhemoglobin (O₂Hb), sodium, potassium, glucose, lactate, oxygen tension at 50% hemoglobin saturation (p50), and bicarbonate. A subgroup analysis was performed to detect the effect of air on results during storage. Percentage deviations were calculated and compared against the preset quality specifications for allowable total error.

Results

At 4°C, pO₂ was the least stable parameter. At 22°C, pO₂ remained stable for 120 min, pH and glucose for 90 min, lactate and pCO₂ for 60 min. Glucose and lactate were stable when chilled. Air bubbles interfered pO₂ regardless of temperatures, whereas pCO₂ increased significantly at 22°C after 30 min, and pH decreased after 90 min. Bicarbonate, sO₂, O₂Hb, sodium, and potassium were the unaffected parameters.

Conclusions

Correct BGA results are essential, and arterial sample is precious. Therefore, if immediate analysis cannot be performed, up to one hour, syringes stored at room temperature will give reliable results when care is taken to minimize air within the blood gas specimen.

Blood Sample Transportation by Pneumatic Transportation Systems: A Systematic Literature Review

BACKGROUND

Pneumatic transportation systems (PTSs) are increasingly used for transportation of blood samples to the core laboratory. Many studies have investigated the impact of these systems on different types of analyses, but to elucidate whether PTSs in general are safe for transportation of blood samples, existing literature on the subject was systematically assessed.

METHODS

A systematic literature review was conducted following the preferred reporting items for systematic reviews and metaanalyses (PRISMA) Statement guidelines to gather studies investigating the impact of PTS on analyses in blood samples. Studies were extracted from PubMed and Embase. The search period ended November 2016.

RESULTS

A total of 39 studies were retrieved. Of these, only 12 studies were conducted on inpatients, mainly intensive care unit patients. Blood gases, hematology, and clinical chemistry were well investigated, whereas coagulation, rotational thromboelastometry, and platelet function in acutely ill patients were addressed by only 1 study each. Only a few parameters were affected in a clinically significant way (clotting time parameter in extrinsic system thromboelastometry, pO2 in blood gas, multiplate analysis, and the hemolysis index).

CONCLUSIONS

Owing to their high degree of heterogeneity, the retrieved studies were unable to supply evidence for the safety of using PTSs for blood sample transportation. In consequence, laboratories need to measure and document the actual acceleration forces in their existing PTS, instituting quality target thresholds for these measurements such as acceleration vector sums. Computer modeling might be applied to the evaluation of future PTS installations. With the increasing use of PTS, a harmonized, international recommendation on this topic is warranted.

Comparison of pneumatic tube system with manual transport for routine chemistry, hematology, coagulation and blood gas tests

BACKGROUND

The pneumatic tube system (PTS) is commonly used in modern clinical laboratories to provide quick specimen delivery. However, its impact on sample integrity and laboratory testing results are still debatable. In addition, each PTS installation and configuration is unique to its institution. We sought to validate our Swisslog PTS by comparing routine chemistry, hematology, coagulation and blood gas test results and sample integrity indices between duplicate samples transported either manually or by PTS.

METHODS

Duplicate samples were delivered to the core laboratory manually by human courier or via the Swisslog PTS. Head-to-head comparisons of 48 routine chemistry, hematology, coagulation and blood gas laboratory tests, and three sample integrity indices were conducted on 41 healthy volunteers and 61 adult patients.

RESULTS

The PTS showed no impact on sample hemolysis, lipemia, or icterus indices (all p<0.05). Although alkaline phosphatase, total bilirubin and hemoglobin reached statistical significance (p=0.009, 0.027 and 0.012, respectively), all had very low average bias which ranged from 0.01% to 2%. Potassium, total hemoglobin and percent deoxyhemoglobin were statistically significant for the neonatal capillary tube study (p=0.011, 0.033 and 0.041, respectively) but no biases greater than ±4% were identified for these parameters. All observed differences of these 48 laboratory tests were not clinically significant.

CONCLUSIONS

The modern PTS investigated in this study is acceptable for reliable sample delivery for routine chemistry, hematology, coagulation and blood gas (in syringe and capillary tube) laboratory tests.

Influence of pneumatic tube system transport on routinely assessed and spectrophotometric cerebrospinal fluid parameters

BACKGROUND

Pneumatic tube systems (PTS) are widely used in many hospitals. Using PTS reduces turnaround time (TAT) and can improve patients' outcome.

METHODS

We investigated whether clinically significant differences could be observed in CSF samples transported by pneumatic tube in comparison with samples transported by hand. Two aliquots from one sample were sent by PTS and by hand from the department of neurology or neurosurgery and compared.

RESULTS

Routine cytological and biochemical assessment was compared in 27 cases. There were no statistically significant changes (transport by hand vs. PTS) in glucose levels [data are expressed as median (minimum-maximum)] at 3.7 (2.5-8.6) mmol/L vs. 3.6 (2.7-8.6) mmol/L, p=0.96 or lactate levels at 1.8 mmol/L (1.1-5.5) vs. 1.8 mmol/L (1.1-5.4). We observed a statistically significant decline in total protein levels in samples transported by PTS at 0.56 g/L (0.19-4.29) vs. 0.49 g/L (0.18-4.3), p=0.008. We observed no changes in erythrocyte count at 5/μL (0-40,000) vs. 5/μL (0-40,106), mononuclear cells at 2/μL (1-145) vs. 3/μL (1-152), or polynuclear cells at 0/μL (0-235) vs. 0/μL (0-352). Spectrophotometric examination was performed in 20 cases. There were no statistically significant differences (transport by hand vs. transport by PTS) in NOA at 0.002 (0.001-1.537) vs. 0.001 (0.001-1.528), p=0.95 or NBA at 0.001 (0.001-0.231) vs. 0.001 (0.001-0.276), p=0.675. Samples transported by PTS were delivered faster than samples transported by courier (transport by hand vs. PTS) at 25 min (10-153) vs. 15 min (4-110), p=0.002.

CONCLUSIONS

We found no significant changes in glucose, lactate levels and in any of the cytological parameters assessed, nor were statistically significant changes observed in the spectrophotometric parameters. We found a statistically significant decrease in total protein levels in samples transported by PTS. Transport by PTS can be faster than transport by hand.

The effects of transport by pneumatic tube system on blood cell count, erythrocyte sedimentation and coagulation tests

Introduction:

Today, the pneumatic tube transport system (PTS) is used frequently because of its advantages related to timing and speed. However, the impact of various types of PTS on blood components is unknown. The aim of this study was to examine the influence of PTS on the quality of routine blood cell counts, erythrocyte sedimentation, and certain blood coagulation tests.

Materials and methods:

Paired blood samples were obtained from each of 45 human volunteers and evaluated by blood cell count, erythrocyte sedimentation, and several coagulation tests, including prothrombin time (PT) and activated partial thromboplastin time (aPTT). Blood samples were divided into 2 groups: Samples from group 1 were transported to the laboratory via the PTS, and samples from group 2 were transported to the laboratory manually. Both groups were evaluated immediately by the tests listed above.

Results:

The blood sample test results from groups 1 and 2 were evaluated and compared. No statistically significant differences were observed (P = 0.069–0.977).

Conclusion:

The PTS yielded no observable effects on blood cell counts, erythrocyte sedimentation, or PT and aPTT test results. We concluded that the PTS can be used to transport blood samples and yield reliable results for blood cell counts, erythrocyte sedimentation, and several coagulation tests.

Preanalytical considerations in blood gas analysis

Blood gas testing is a commonly ordered test in hospital settings, where the results almost always have the potential to dictate an immediate or urgent response. The preanalytical steps in testing, from choosing the correct tests to ensuring the specimen is introduced into the instrument correctly, must be perfectly coordinated to ensure that the patient receives appropriate and timely therapy in response to the analytical results. While many of the preanalytical steps in blood gas testing are common to all laboratory tests, such as accurate specimen labeling, some are unique to this testing because of the physicochemical properties of the analytes being measured. The common sources of preanalytical variation in blood gas testing are reviewed here.