| Kanchan Jeswani |
The CBC count – the most frequently requested clinical laboratory tests is processed accurately in automated haematology analysers. During the last two decades, automated blood cell counters have undergone a formidable technological evolution owing to the introduction of new physical principles for cellular analysis and the progressive evolution of software. The results have been an improvement in analytic efficiency and an increase in information provided, which, however, require ever more specialised knowledge to best discern the possible clinical applications.
Today’s analysers are able to provide much more information, quantitative such as the extended parameters and qualitative ie. suspect flags. Scatterplots and histograms of the real-time data provide an insight regarding abnormal population of cells and disease patterns which can be identified by the haematologist. These advanced features help in reducing manual reviews, thereby improving the turnaround time for the physicians. The correct interpretation of results requires extensive knowledge of the analytic performance of the instruments and the clinical significance of the results reported.
Complete blood count –The 3D approach
- Traditional parameters of the CBC count and differential count
These are the conventional, essential parameters reported since time immemorial.
- Advanced clinical parameters
The new generation analysers’ technology have developed advanced clinical parameters to assess their clinical utility and are approved for routine use in almost all cell lineages.
Red cells: Response to treatment can be monitored using Reticulocyte Haemoglobin Content and Immature Reticulocyte Fraction to differentiate between classical and functional iron deficiencies, in addition to monitoring of EPO and/or intravenous iron administration. Suspect flags for red cell abnormality are displayed such as red cell agglutinins and fragmented red cells.
White cells: New positional parameters such as Immature Granulocytes provide prior information on bacterial inflammation. White cell counts are corrected for the presence of NRBC and the NRBC enumeration is reported with every sample. Suspect flags are identified for left shift, abnormal/atypical lymphocyte ,blast, etc.
Platelets: Immature Reticulated Platelets (IPF per cent Immature platelet fraction) distinguish between the causes of thrombocytopenia- increased consumption or decreased production. It also predicts the timing of platelet recovery (after transplantation or chemotherapy) thereby preventing unnecessary platelet transfusions- a precious resource and avoids potential infection risk. Suspect flags are generated for giant platelets, platelet clumps and cellular interferences.
- Non-reportable research parameters
These parameters have started to emerge as useful tool in predicting the presence of infections (bacterial/viral); neonatal sepsis; malignancy; inflammation and parasites in blood to name a few. The eventual incorporation of a ‘malaria alert’ into all modern analysers (now available as suspect flags) would allow for an automated and adjuvant diagnostic method in the work-up of febrile patients possibly infected with malaria, especially in scenarios with low pre-test probability for the disease.
Some of the high end haematology analysers are equipped with a body fluid mode for reporting red cell counts, total nucleated cell counts and differentials. Rerun/reflex testing is done automatically without user intervention based on decision rules incorporated in the system. These advanced features helps in reducing manual reviews significantly thereby bettering the turnaround time for the physicians and timely care for the patients.
Quality assurance
Internal Quality Control and External Quality Assurance Schemes are readily available for conventional parameters. It is good laboratory practice to have accredited External Quality Assessment Schemes (EQAS) for the reportable clinical parameters as well. For a number of parameters,on some instruments, there is no internal quality control, which brings into question whether these parameters should be used for clinical decision making. It is important to establish reference ranges locally, and sites wishing to utilise these parameters need to ensure that their analysers are fully optimised and standardised before use. Laboratories with more than one instrument of the same type need to standardise settings between instruments as well on a regular basis.
Futuristic automation
Automation is going the modular way with multiple units of haematology analysers, integrable slide-maker/stainer, digital morphology system, tube sorters, automated ESR systems, HbA1c system linked to the middle-ware and LIS, making it a true walkaway one lavender top system.
Conclusion
Automated blood cell counters are becoming more sophisticated and the range of reportable parameters available is ever increasing. There are increasing amounts of data provided, which require specialist knowledge to interpret as well as understand the limitations in the measurement of the parameters. Both haematologists and clinicians need to remain updated with new parameters and interpretations. Good laboratory practice ensures that reliable results of clinically relevant laboratory tests are reported to the clinician. This expanding range of parameters does allow for novel applications and introduces an element of research and development into routine laboratory haematology practice.