Editor: Deborah Sesok-Pizzini, MD, MBA, professor, Department of Clinical Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, and chief, Division of Transfusion Medicine, Children’s Hospital of Philadelphia.
A logical delta check for identifying erroneous blood cell count results
Regulations require that hospitals have a quality management plan that benchmarks key indicators of quality performance. One such indicator is a delta check, which is a broad quality control for preanalytic and analytic errors that identifies significant variation in a patient’s present lab result when compared with the patient’s previous result for the same test. The author conducted a study that involved implementing an effective and practical complete blood cell count (CBC) delta check by optimizing specificity and sensitivity using weighed deltas of multiple parameters. The mean red blood cell volume (MCV) delta (greater than 3.0 fL) check was retrospectively assessed on 110 days between November 2010 and March 2011. The composite CBC delta (CCD) test was then formulated using serial same-patient CBC data and random interpatient CBCs. This was followed by a logical delta check, which ignores CCD failures due to platelet change only. The author’s results showed that the MCV delta check test recognized only three of the six mislabeled specimens in the initial review period, whereas the CCD identified all of them. The logical delta check flagged two percent of eligible results, one-third as many as the MCV delta check. Furthermore, the CCD and logical delta checks revealed 20 presumed or confirmed mislabeling events, only half of which were identified by the MCV delta check. The study showed that the MCV delta check test was not as useful as the logical delta check for correcting errors in the laboratory due to low specificity and sensitivity. The logical delta check was demonstrated to be a more useful tool in identifying preanalytic and analytic specimen problems, including specimens labeled with the wrong name.
Miller I. Development and evaluation of a logical delta check for identifying erroneous blood count results in a tertiary care hospital. Arch Pathol Lab Med. 2015;139:1042–1047.
Correspondence: Dr. Ira Miller at [email protected]
Drop-to-drop variation in fingerprick blood: relevance to POC diagnostics development
Because blood obtained via fingerprick is commonly used in point-of-care assays, it is important to understand the drop-to-drop variation obtained from fingerprick blood. The authors conducted a study to determine the minimum amount of blood needed to reduce variability to acceptable levels for clinical decision-making. They analyzed hemoglobin concentration, total white blood cell count, three-part WBC differential (lymphocytes, monocytes, and granulocytes), and platelet count in six successive drops. Blood was collected from one fingerprick (20 μL each) and analyzed using a hematology analyzer, and venous blood was used as a comparison. The authors also studied the variability of the hemoglobin concentration of 10 successive drops (10 μL each) of fingerprick blood measured using a point-of-care hemoglobinometer. The results showed that the average percent coefficient of variation (CV) for successive drops of fingerprick blood was higher by up to 3.4 times for hemoglobin, 5.7 times for WBC count, three times for lymphocyte count, 7.7 times for granulocyte count, and four times for platelets as compared to venous controls when using a hematology analyzer. The average percent CV for fingerprick blood was up to five times higher for hemoglobin than venous blood using point-of-care testing methods. The authors concluded that this data suggest the need for caution when using fingerprick blood to obtain hemoglobin and WBC results that will be used in clinical decision-making. They noted that clinicians need to either accept the inaccuracy inherent in using fingerprick blood on these devices as a trade-off for ease of blood collection, or they need to collect, read, and average multiple fingerprick samples, or simply collect and analyze venous blood.
Bond MM, Richards-Kortum RR. Drop-to-drop variation in the cellular components of fingerprick blood. Implications for point-of-care diagnostic development. Am J Clin Pathol. 2015;144:885–894.
Correspondence: Dr. Rebecca R. Richards-Kortum at [email protected]