Preanalytical Errors Introduced by Sample-Transportation Systems: A Means to Assess Them

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.

Current Practice and Regional Variability in Recommendations for Patient Preparation for Laboratory Testing in Primary Care

BACKGROUND

Preparation of the patient for laboratory tests is crucial. Our aim was to investigate the current practice and regional variability of recommendations regarding patient preparation for laboratory testing.

METHODS

A call for data was posted by email. Spanish laboratories were invited to fill out and submit a survey.

RESULTS

Sixty-eight laboratories participated in the study. In 73% of those laboratories, fasting was always recommended regardless of the requested tests. Only one-third of the laboratories systematically recommended a 12-hour fast before the tests. In 71% of the laboratories, water intake was allowed without restrictions during the fasting period. In 57% of the laboratories, computerized order entry offered the possibility to print customized recommendations automatically in the primary care doctor's office according to the requested tests. Seventy-two percent of the laboratories agreed with the proposed recommendation.

CONCLUSIONS

There was high variability in patient preparation for laboratory testing. A significant proportion of centers did not follow international guidelines.

The effects of transport by car on coagulation tests

Background:

This research investigated the effects of the transport of blood samples between centers/laboratories by car on coagulation tests.

Methods:

Five tubes of blood samples were taken from 20 healthy volunteers. The samples consisted of a baseline (control) group, centrifuged and noncentrifuged transported samples; centrifuged and noncentrifuged untransported samples. The groups of centrifuged and noncentrifuged samples were transported by car for 2 h. The centrifuged and noncentrifuged untransported samples were incubated in the laboratory until the transported samples arrived. Prothrombin time (PT) and activated partial thromboplastin time (APTT) tests were conducted for all samples.

Results:

Significant differences between the baseline group and the centrifuged and noncentrifuged transported samples and the noncentrifuged untransported samples were found for APTT levels (p<0.05, for all). In addition, significant mean percentage differences in PT values were found between the baseline group and the noncentrifuged transported samples (p<0.001) and the noncentrifuged untransported samples (p=0.005). The mean level of PT in the noncentrifuged transported samples was outside the upper limit of the clinical decision level.

Conclusions:

Noncentrifuged transported samples showed clinically significant differences in PT test results that may have stemmed from mechanical agitation during transportation. Therefore, we recommend not transporting noncentrifuged specimens for PT testing by car.

Heparinate but not serum tubes are susceptible to hemolysis by pneumatic tube transportation

Background:

Pneumatic tube transportation (PTT) may induce hemolysis (H) in blood samples. We aimed to compare the H degree before and after PTT implementation in our hospital.

Methods:

Hemolysis indices (HI) for all lithium-heparin plasma samples (P) drawn by the Emergency Department in 2-month periods were retrospectively collected and pre- (n=3579) and post-PTT (n=3469) results compared. The impact of PTT introduction was investigated on LDH [HI threshold (HIt), 25], conjugated bilirubin (cBIL) (HIt, 30), K (HIt, 100) and ALT (HIt, 125). In addition, HI retrieved for P and paired serum samples collected in silica clot activator tubes (S) from the same venipuncture were compared in pre- (n=501) and post-PTT (n=509) periods.

Results:

Median (5–95th percentile) HI in P was significantly higher in post-PTT period [7 (0–112) vs. 6 (0–82), p<0.001]. Results reported as ‘Hemolysis’ in P increased from 6.6% in pre-PTT to 9.4% in post-PTT (p<0.001). Investigated tests gave the following rejection rates (pre-PTT vs. post-PTT): LDH, 13.4% vs. 18.8%, p<0.001; cBIL, 9.4% vs. 27.0%, p<0.05; K, 3.7% vs. 5.6%, p<0.001; ALT, 2.9% vs. 4.4%, p<0.01. The slightly higher susceptibility to H of S compared to paired P found in the pre-PTT [9 (1–64) vs. 6 (0–85)] was not confirmed in the post-PTT period [7 (0–90) vs. 8 (1–72)], in which median HI in S was significantly lower (p<0.001) than in pre-PTT.

Conclusions:

In our setting PTT promotes H in P, increasing the rate of rejected tests. The use of S appears to protect against the hemolysing effect of PTT.

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.

Random variation and systematic error caused by various preanalytical variables, estimated by linear mixed-effects models

BACKGROUND

We wanted to determine whether specific, preanalytical sample handling increases preanalytical variation and bias test results compared with optimal handling.

METHODS

Blood was collected into 4 serum-separation tubes from each arm of 60 outpatients. In 30 of the patients, half of the tubes were transported in the pneumatic tube system, while the other half were manually delivered. In the remaining patients, the blood samples were collected using 21-gauge straight needles (green needles) and 23-gauge butterfly needles. Half of the tubes were mixed by inverting 5-6 times, and the other half by one inversion. Linear mixed-effects models were used as statistical method.

RESULTS

Transporting samples in the pneumatic tube system caused a significant bias to the results for LD (4.5 U/L, p<0.001) and magnesium (0.0021 mmol/L, p=0.003). For CK and glucose, the preanalytical variation was significantly higher for samples transported in the pneumatic tube system vs manual delivery. Using butterfly needles resulted in lower values (p<0.05) for calcium (-0.0072 mmol/L), CK (-0.75 U/L) and LD (-1.6 U/L) compared with 21-gauge needles. The preanalytical variation for ALP was significantly higher with butterfly needles.

CONCLUSIONS

The specific sample handling had significant but small random and systematic effects on results for some analytes.