Point-of-care device shows promise for blood eosinophil count in severe asthma
medwireNews: Study findings validate a point-of-care (POC) device for assessing blood eosinophils that could help in the management of severe asthma.
“[T]he possibility of assessing biomarkers in a [POC] modality (as is already possible for FeNO [fractional exhaled nitric oxide]) could accelerate the time needed to define, in a noninvasive way, the severe asthma phenotype and therefore anticipate the choice of the most suitable biologic treatment,” say the researchers led by Enrico Heffler (Humanitas University, Milan, Italy).
They tested the HemoCue WBC Diff (HemoCue AB, Ängelholm, Sweden) portable POC device, which quantifies the total white blood cell (WBC) count in capillary whole blood from a single drop of blood collected with a finger prick. The device also provides a differential count of absolute and percentages of neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
The device gave very similar blood cell count measurements to that of a conventional complete blood cell (CBC) count analyzer when in tested in 76 patients who had severe asthma, according to the European Respiratory Society /American Thoracic Society guidelines, and had not experienced an exacerbation or respiratory infection in the past month.
The only significant differences between the two devices were for mean neutrophil and eosinophil counts, which were significantly higher using the CBC count analyzer, compared with the HemoCue WBC Diff.
Nevertheless, the correlation between the two devices for blood eosinophils was significant, at 85%, with similar significant correlations also seen for WBC count, neutrophils, and lymphocytes, at 80%, 79%, and 69%, respectively.
In predicting concomitant airway eosinophilia, based on the ELEN index (a composite score comparing ratios of eosinophils/lymphocytes and eosinophils/neutrophils), the CBC count analyzer and the HemoCue WBC Diff were in agreement for 43.4% of patients.
For this index, the POC device had an accuracy rate of 82.2%, with a sensitivity and specificity of 71.7% and 100%, respectively.
It had a similar predictive ability for eosinophil count cutoffs commonly used in large trials for biologic treatments, with area under the receiver operating characteristic curves of 0.918 for an eosinophil count above 150 cells/µL, 0.905 for counts above 260 cells/µL, 0.946 for counts above 300 cells/µL, and 0.964 for counts above 400 cells/µL.
Heffler and colleagues say the findings “may open the possibility of using POC technology to assess one of the main biomarkers for severe asthma management: blood eosinophil count.”
They add that if used in addition to other currently available instruments, such as a spirometer and FeNO portable analyzer, more sophisticated descriptions of severe asthma phenotypes could be obtained and, as a result, allow more precise prescription of biologic therapies in the shortest possible time.
“These achievements may really bring respiratory medicine, as a discipline, close to the concept of personalized medicine,” they conclude in the Annals of Allergy, Asthma & Immunology.
By Lucy Piper
medwireNews is an independent medical news service provided by Springer Healthcare. © 2017 Springer Healthcare part of the Springer Nature group