Hematology instruments have emerged as irreplaceable diagnostic tools used in testing, counting, measuring, and analyzing red blood cells, WBC, and platelets. Hematology instruments evolved rapidly from traditional instruments to present-day sophisticated automated instruments that provide fast and accurate results. Automation is a growing trend in hematology instruments with the laboratories following a shift from manual testing to semi-automated analyzers and to fully automated analyzers. Market players have been observed to invest heavily in product development to offer user-friendly, more sophisticated, efficient, and accurate analyzers to meet the demands of hospitals and clinics. Automated systems play a crucial role in transfusion medicines and facilitate screening of blood donors as well as quality control of blood products. Manufacturers today have developed hematology analyzers that achieve good levels of precision and accuracy in cell counting through examination and identification of thousands, not hundreds, of cells in each sample analyzed.
Demand for core lab automation is seemingly unquenchable, limited only by the diminishing compromises to testing accuracy, sensitivity, or reliability. The last domain in lab hematology outside the reach of automation has been manual review and manual differentials. The discriminatory abilities of impedance- and laser light scatter-based analyzers has limitations such as sampling errors, calibration errors, interfering substances, and the absence of distinguishing cell features detectable by volume or light scatter. Automated visual analysis overcomes the limitations of analyzer differentials and potential errors of laborious manual differentials. Manual review of slides with stained blood samples is taxing in terms of lab personnel's time and its estimation principles are limited compared to high-speed neural networking available on digital cell imaging platforms. Automation is becoming increasingly indispensible to labs managing relatively high volumes of flagged blood samples.
Automated blood cell counters have delivered significant improvements in speed and accuracy of cellular blood analysis, using optical light scattering or changes in electrical current induced by blood cells flowing through an electrically charged small opening. There is a tendency for new hematology analyzers to employ increasingly more detectors than the older models, for improved specificity in cell classification, and for more accurate flagging of abnormal blood cells. Modern automated hematology instruments use optical methods (light scatter), impedance-based methods based on the Coulter principle, or a combination of both optical and impedance-based methods.
Due to its technical simplicity, impedance technology is widely used in simple bedside/point-of-care instruments to generate a 3-part WBC differential, along with RBC and platelet (PLT) counts.Â Platelet analysis using an improved optical technology is less prone to interference than impedance technology. Using detectors that are placed under different angles relative to the incoming laser light, this technology allows measurement of different aspects of blood cells simultaneously. Polarized light measurement also is an aid in differentiating neutrophils and eosinophils because the latter are normally the only blood cells that have the capacity of disturbing the polarization of the laser beam. Another technological advance was the use of fluorescence by a nuclear stain for identifying and enumerating nucleated RBC, apart from WBC. In the latest generation of analyzers, nuclear fluorescence is combined with light scatter and radiofrequency for constructing a 5-part WBC differential.
Imaging for hematology is still in its infancy. The accuracy and precision of pre-classifier devices will be improved through innovations in algorithm development, but deriving cell counts and hemoglobin measurement from a smear remain significant technical challenges can be expected to take some time to solve. Increasing throughput on imaging devices is another challenge that will need to be solved before such instruments can replace conventional analyzers.
Digital imaging of traditionally stained blood cells on a glass slide is gaining widespread use now that digital cameras and powerful computers have become more affordable. Imaging solution based upon ink-jet volumetric printing of blood cells on a slide and then staining them and subsequently analyzing the pictures using digitalized pattern recognition. Another solution for point-of-care hematology testing uses a compact device that images blood cells suspended in a counting chamber after staining with fluorescent dye. Â
Progressive improvement in these instruments has allowed cost-effective enumeration and evaluation of blood cells with great accuracy and precision. There is a continued focus on the addition of new parameters and the development of point-of-care instrumentation in hematology. In the future, in-vivo analysis of blood cells may allow non-invasive and near-continuous measurements.
Analyzers are being integrated onto fully automated hematology lines to report results that can be used as a part of an auto-verification system for reporting CBC and differential results with minimal review time. Cell image analyzers promote a more standardized differential result throughout a single laboratory or an entire integrated healthcare network. Differential workflow has traditionally been a challenge, especially when dealing with leukopenic samples. Automated cell image analyzers typically have the ability to merge multiple slides made from low white count samples into a single case, eliminating the need for a buffy coat preparation prior to a manual differential.
Automation helps to remove the inherent subjectivity demonstrated with manual microscopic analyses. The vendors are expected to introduce improved algorithms, detection systems, and reagents to improve blast, immature granulocyte, and NRBC detection, which will further improve FPE. Another major theme for development will be automation with the use of robots and tracks to move samples around the laboratory; andÂ simplification of interfaces on instruments to harmonize training needs.
In the near term, information technology will play a growing role as an adjunct to technological developments in hematology analyzers. Advanced information technology could be useful for unveiling information that is hidden in signals that register, but currently are used only for cell counting and classification. Blood-cell analysis will become more multi-dimensional, and this multitude of cellular information will rapidly expand. A more detailed look into the characteristics of a certain cell can possibly yield more information than just WBC, such as data associated with cellular activation pathways and apoptosis or other cellular processes.
As consolidation in path labs continues, a polarized testing environment is expected to develop. On the one hand, there will be fewer large centralized testing facilities, with satellite labs offering a limited or stat menu in the ER, ICUs, and specialized clinics. The needs of consolidated and satellite labs are different and will require customized approaches by manufacturers to meet them. Larger labs will need high throughput instruments and automated rules-based reflex testing. In the foreseeable future, hematology testing may not be characterized as much by technology innovation but in finding ways to perform higher volumes of highly accurate routine and follow-up tests in both traditional laboratories and alternative care sites.