Prolonged storage-induced changes in haematology parameters referred for testing.

Elise Schapkaitz,Dashini Pillay

doi:10.4102/ajlm.v4i1.208

Abstract

Referral of samples for the work-up of haematological disorders from remote laboratories can result in a delay in analysis. The stability of the full blood count (FBC), differential count (DIFF), reticulocyte and peripheral blood smear (PBS) morphology during extended storage was evaluated. Forty blood samples stored in ethylenediaminetetraacetic acid (EDTA) were analysed on an ADVIA® 120 haematology analyser. The samples (25% abnormal; 75% normal) were stored at room temperature (RT) and at 4 °C - 8 °C. Analysis of samples stored at RT was performed every 12 hours for two days. Analysis of samples stored at 4 °C - 8 °C was performed at 12 hours and subsequently every 24 hours for seven days. FBC parameters (red cell count, haemoglobin) and DIFF parameters (percentages of basophils, lymphocytes and monocytes) were stable for at least 48 hours when stored at RT. Platelets were only stable for 12 hours and the white cell count was stable for 36 hours when stored at RT. Storing samples at 4 °C - 8 °C significantly increased the stability of most parameters, in particular, mean cell volume and percentage of reticulocytes. However, DIFF parameters were associated with lower stability at 4 °C - 8 °C. PBS morphology was compromised prior to 12 hours whether stored at RT or at 4 °C - 8 °C. This study provides evidence that blood samples stored in EDTA at 4 °C - 8 °C for seven days are suitable for testing on the ADVIA® 120 analyser for the FBC and percentage of reticulocyte parameters. However, storage at 4 °C - 8 °C is not a solution for samples referred for DIFF and PBS morphology review.

Highlights

Pre-analytical variables, such as storage time and temperature, affect the measurement of laboratory parameters collected in ethylenediaminetetraacetic acid (EDTA).[1,2] Laboratory staff need to be aware of the changes that occur during storage in their specific setting in order to decide whether to accept or reject samples that are too old to obtain reliable results
Red cell parameters including red cell count (RCC), haemoglobin, mean cell haemoglobin (MCH) and red cell distribution width (RDW) were stable for at least 48 hours after collection when stored at room temperature (RT) and were not significantly affected by storage temperature
The mean percentage difference for full blood count, differential count and reticulocyte count was plotted against time in hours from the value at time zero

Summary

Introduction

Pre-analytical variables, such as storage time and temperature, affect the measurement of laboratory parameters collected in ethylenediaminetetraacetic acid (EDTA).[1,2] Laboratory staff need to be aware of the changes that occur during storage in their specific setting in order to decide whether to accept or reject samples that are too old to obtain reliable results. It is recommended that traditional FBC parameters such as red cell count (RCC), white cell count (WCC), haemoglobin and platelet count be analysed 24 hours after sample collection when stored at room temperature (RT).[3,4,5] parameters useful for diagnosis and monitoring of haematological disorders, such as mean cell volume (MCV), reticulocyte and PBS morphology, are unreliable after 12 hours.[5] Osmotic swelling of red cells during storage at RT affects volume-dependant variables and results in misclassification of a microcytic anaemia as normocytic and, a normocytic anaemia as macrocytic.[6] Reticulocytes mature into red cells after 24 hours in circulation. Referral of samples for the work-up of haematological disorders from remote laboratories can result in a delay in analysis

Results

Discussion

Conclusion