Unreliable Automated Complete Blood Count Results: Causes, Recognition, and Resolution.

Automated hematology analyzers generate accurate complete blood counts (CBC) results on nearly all specimens. However, every laboratory encounters, at times, some specimens that yield no or inaccurate result(s) for one or more CBC parameters even when the analyzer is functioning properly and the manufacturer's instructions are followed to the letter. Inaccurate results, which may adversely affect patient care, are clinically unreliable and require the attention of laboratory professionals. Laboratory professionals must recognize unreliable results, determine the possible cause(s), and be acquainted with the ways to obtain reliable results on such specimens. We present a concise overview of the known causes of unreliable automated CBC results, ways to recognize them, and means commonly utilized to obtain reliable results. Some examples of unreliable automated CBC results are also illustrated. Pertinent analyzer-specific information can be found in the manufacturers' operating manuals.

The Results of Hemoglobin Variant Analysis in Patients Revealing Microcytic Erythrocytosis on Complete Blood Count.

BACKGROUND: Microcytic erythrocytosis is an underrecognized and underevaluated complete blood count (CBC) finding. The literature pertaining to the determination of its etiology specifically by hemoglobin variant analysis is limited. METHODS: We performed hemoglobin variant analysis by high performance liquid chromatography on 137 patients who revealed microcytic erythrocytosis on CBC, and reviewed the results for the diagnosis of hemoglobin-associated disorders. RESULTS: A diagnosis of thalassemia trait and/or a hemoglobinopathy was established in 93 of 137 (67.9%) patients. Amongst these, ß-thalassemia trait topped the list with 69 cases (74.1%), followed by hereditary persistence of fetal hemoglobin with 5 cases (5.5%), Hemoglobin E disease with 4 cases (4.3%), and ∂/ß-thalassemia with 2 cases (2.1%). Compound heterozygous conditions with 1 or more hemoglobinopathies and/or thalassemias were diagnosed in 13 cases (14.0%). Abnormal hemoglobins in the compound heterozygosity group included C, S, HPFH, and 2 unknowns. CONCLUSION: Hemoglobin variant analysis provided a very high positive yield in determining the etiology of microcytic erythrocytosis.

Feasibility of Counting Smudge Cells as Lymphocytes in Differential Leukocyte Counts Performed on Blood Smears of Patients With Established or Suspected Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma.

BACKGROUND: Lymphocytosis and smudge cells are commonly observed on the blood smears of patients with an established or suspected diagnosis of chronic lymphocytic leukemia/small lymphocytic lymphoma. Excluding smudge cells from the manual differential count (MDIFF), a common laboratory practice, yields unreliable results and consequently necessitates performing the MDIFF testing on an albuminized blood smear. OBJECTIVE: To assess the reliability of counting smudge cells as lymphocytes in the MDIFFs on nonalbuminized smears and automated differentials (ADIFFs) as a substitute for MDIFFs. METHODS: We compared corresponding results of MDIFFs on nonalbuminized smears vs MDIFFs on albuminized smears (group A, n = 82), ADIFFs vs MDIFFs on nonalbuminized smears (group B, n = 68), and ADIFF vs MDIFFs on albuminized smears (group C, n = 50). Smudge cells on the nonalbuminized smears were counted as lymphocytes. We focused on 2 white blood cell types: neutrophils and lymphocytes. RESULTS: Respective means for % lymphocytes and % neutrophils were 83.2 vs 83.2 and 14.0 vs 13.6 for Group A, 75.0 vs 77.0 and 20.2 vs 19.8 for Group B, and 76.1 vs 79.3 and 18.7 vs 17.4 for Group C. Respective correlation coefficients for % lymphocytes and % neutrophils were 0.92 and 0.94 for group A, 0.94 and 0.97 for group B, and 0.88 and 0.92 for group C. CONCLUSION: Counting smudge cells as lymphocytes on nonalbuminized blood smears yielded reliable MDIFF results. Reportable ADIFF results were generated by the analyzer on 73% of the specimens, of which 93% were reliable.

Assessment of the Reliability of the Sysmex XE-5000 Analyzer to Detect Platelet Clumps.

OBJECTIVE: Platelet counts generated by automated analyzers on blood specimens that contain platelet clumps are often inaccurate and require verification by blood-smear review. In this study, we assessed the reliability of the Sysmex XE-5000 instrument to detect platelet clumps. METHOD: We reviewed automated complete blood count (CBC) results and the findings of the microscopic review of corresponding blood smears of 600 blood specimens specifically selected from the routine laboratory workload. The sensitivity, specificity, efficiency, positive predictive value (PPV), and negative predictive value (NPV) of its 2 platelet-associated flags (abnormal platelet-size distribution [PAD] flag and platelet-clumps [CLP] flag) were determined. RESULTS: The respective values for the sensitivity, specificity, efficiency, and PPV were 42%, 83%, 63%, and 1% for the PAD flag and 57%, 99%, 78%, and 37% for the CLP flag. The NPV was 100%. CONCLUSION: The overall reliability of the CLP flag is superior than that of the PAD flag but there is room for further improvement.

Detection of Platelet Clumps on Peripheral Blood Smears by CellaVision DM96 System and Microscopic Review.

OBJECTIVE: To determine and optimize the sensitivity of the CellaVision DM96 automated image-analysis system in detecting platelet (PLT) clumps on blood smears and to assess the reliability of the traditional laboratory practice of examining only the feather edge of the smear for PLT clumps. METHODS: We processed 102 blood smears that revealed PLT clumps on microscopic review, using the CellaVision DM96, and reviewed the results for the ability of the analyzer to detect these clumps. We obtained the data regarding relative distribution of PLT clumps on different parts of the blood smear (feather edge, lateral edges, and readable area) from our microscopic-review observations. RESULTS: The sensitivity of the Cellavision DM96 in detecting PLT clumps was between 40.4% and 82.8%, depending on the number of screens reviewed for this variable. Via microscopic review of the smears, the PLT-clump detection rate increased from 85.3%, obtained by examining only the feather edge, to 99.0%, obtained by examining the feather edge plus the readable area. CONCLUSION: The sensitivity of the DM96 for detecting PLT clumps can be maximized to 82.8% by reviewing the entire white blood cell screen and the entire PLT screen. Microscopic review of the blood smears yielded a PLT-clump detection rate of 99.0% when we examined the feather edge and the readable area of the smear.

Purpose and criteria for blood smear scan, blood smear examination, and blood smear review.

A microscopic examination of an appropriately prepared and well-stained blood smear by a knowledgeable laboratory professional is necessary and clinically useful in a number of circumstances and for a variety of reasons. In this article, an attempt is made to delineate the purpose and criteria for blood smear examination in a variety of circumstances that are encountered in everyday laboratory hematology practice. A blood smear scan serves to at least (a) verify the flagged automated hematology results and (b) determine if a manual differential leukocyte count needs to be performed. Blood smear examination/manual differential leukocyte count with complete blood count (CBC) provides the complete hematologic picture of the case, at least from the morphologic standpoint. Blood smear review with or without interpretation serves to ensure that no clinically significant finding is missed, besides providing diagnosis or diagnostic clue(s), particularly if and when interpreted by a physician.

Does routine repeat testing of critical values offer any advantage over single testing?

CONTEXT: Before being communicated to the caregiver, critical laboratory values are verified by repeat testing to ensure their accuracy and to avoid reporting false or erroneous results. OBJECTIVE: To determine whether 2 testing runs offered any advantage over a single testing run in ensuring accuracy or in avoiding the reporting of false or erroneous results. DESIGN: Within the hematology laboratory, 5 tests were selected: hemoglobin level, white blood cell count, platelet count, prothrombin time, and activated partial thromboplastin time. A minimum of 500 consecutive critical laboratory test values were collected retrospectively for each test category. The absolute value and the percentage of change between the 2 testing runs for each critical value were calculated and averaged for each test category and then compared with our laboratory's preset, acceptable tolerance limits for reruns. RESULTS: The mean results obtained for the absolute value and the percentage of change between the testing runs were 0.08 g/dL (1.4%) for hemoglobin levels, 50 cells/µL (10.2%) for white blood cell counts, 1500 cells/µL (9.9%) for platelet counts, 0.7 seconds (1.4%) for prothrombin time, and 5.1 seconds (4.4%) for activated partial thromboplastin time (all within our laboratory's acceptable tolerance limits for reruns). The percentage of specimens with an absolute value or a mean percentage of change outside our laboratory's acceptable tolerance limits for reruns ranged between 0% and 2.2% among the test categories. No false or erroneous results were identified between the 2 testing runs in any category. CONCLUSIONS: Routine, repeat testing of critical hemoglobin level, platelet count, white blood cell count, prothrombin time, and activated partial thromboplastin time results did not offer any advantage over a single run.

International normalized ratio versus plasma levels of coagulation factors in patients on vitamin K antagonist therapy.

CONTEXT: The key question when managing patients on warfarin therapy who present with life-threatening bleeding is how to use the international normalized ratio (INR) to best direct corrective therapy. The corollary question for the clinical laboratory is at what level will the INR reflect a critical value that requires notifying the clinician. OBJECTIVE: To determine the levels of vitamin K-dependent factors over a range of INR values. DESIGN: Evaluation of the vitamin K-dependent coagulation factor levels on plasma remnants from patients in whom a prothrombin time and INR was ordered to monitor warfarin therapy. There were a total of 83 specimens evaluated with an INR range from 1.0 to 8.26. RESULTS: The mean activity levels of all 4 factors remained near or above 50% when the INR was less than 1.5. The average factor X level was 23% when the INR range was 1.6 to 2.5, but levels of factors II, VII, and IX did not drop below the hemostatic range until the INR was greater than 2.5. At an INR of 3.6 or more, the activity levels of all 4 factors were less than 30% in more than 90% of the specimens. CONCLUSION: Levels of factors II, VII, IX, and X declined with increasing INR but not at the same rate and not to the same level at a given INR. However, most of the values were below the hemostatic value once the INR was 3.6 or more, the level that was also considered critical for physician notification.

An evaluation of the performance of Sysmex XE-2100 in enumerating nucleated red cells in peripheral blood.

CONTEXT: Automated methods of enumerating nucleated red blood cells (NRBCs) in blood are gaining acceptance in many laboratories. OBJECTIVE: To evaluate the performance of Sysmex XE-2100 in enumerating NRBCs in peripheral blood. DESIGN: Automated relative number of NRBCs per 100 white blood cells (NRBC%) results for a total of 460 specimens run on the XE-2100 were compared with manual NRBC% results obtained by performing a 100-cell differential on a Wright-stained smear prepared from each specimen. To assess within-day reproducibility, 64 specimens were rerun on the XE-2100, and a second 100-cell differential was performed on the original blood smear. Excel software was used for data analysis. RESULTS: Regression analysis of automated NRBC% versus manual NRBC% yielded a correlation coefficient of 0.9712. No NRBCs were seen in the blood smear on 35 (15.1%) of 232 specimens with automated NRBC% of 0.1 to 1.9. The XE-2100 generated an NRBC% of 0.0 on 5 (6.8%) of 74 specimens, revealing 1 NRBC per 100 or more white blood cells by blood smear examination. The mean percent difference between duplicate automated results was 16.7 compared with 78.1 for the duplicate manual results. There were 9 instances in which the XE-2100 either did not detect the presence of more than 8 NRBCs per 100 white blood cells or generated an automated NRBC% of 18.1 or 18.8 when the smear revealed none. All of these were, however, flagged for smear review. CONCLUSIONS: Overall correlation between the automated and manual results was excellent. The automated method revealed better precision than the manual method. The number of specimens with false automated results was very small, and all were flagged for verification by a smear review.

Changes in automated complete blood cell count and differential leukocyte count results induced by storage of blood at room temperature.

OBJECTIVE: To delineate changes that occur in various parameters of automated complete blood cell count (CBC) and differential leukocyte count (differential) on prolonged storage of blood at room temperature. DESIGN: A CBC and an automated differential were performed on the Coulter Gen.S on 40 K(3) (tripotassium ethylenediamine-tetraacetate) EDTA-anticoagulated blood specimens once daily, specimen volume permitting, for 3 to 7 days. Specimens were kept at room temperature throughout the study. The results were tabulated using a personal computer with Excel software. Percent change or absolute difference from the initial value for each parameter for each subsequent day of the study period was calculated. RESULTS: Among the CBC parameters, hemoglobin, red blood cell count, and mean corpuscular hemoglobin were stable for the duration of the study (7 days), white blood cell count was stable for at least 3 days (up to 7 days, if the count was within or above the normal range), and platelet count was stable for at least 4 days (up to 7 days, if the count was within or above the normal range). The mean corpuscular volume, mean platelet volume, hematocrit, and red blood cell distribution width each increased, and the mean corpuscular hemoglobin concentration decreased from day 2 onward. Among the differential parameters, the relative percentages and absolute numbers of neutrophils, lymphocytes, and eosinophils tended to increase, whereas those of monocytes trended downward over time. Limited data on basophils did not reveal an appreciable change. CONCLUSION: Blood specimens stored at room temperature for more than 1 day (up to 3 days or possibly longer) were found to be acceptable with some limitations for CBC but not for the differential.

Uso del mezclador vortex para disolver agregados plaquetarios

La agregación plaquetaria en la sangre anticoagulada con EDTA es la principal causa de reportes bajos falsos en el recuento plaquetario hecho por contadores electrónicos. para obtener un recuento plaquetario confiable en estos casos, los laboristas con frecuencia recogen posteriormente muestras sanguíneas con citrato o sin anticoagulante. Los pacientes son así sometidos a una segunda punción venosa o capilar, y el reporte de los resultados se retarda. Nuestros datos muestran que se pueden obtener resultados confiables con un equipo automatizado, si las muestra que se observan con agregados plaquetarios bajo el microscopio, son mezcladas con vortex y luego pasadas nuevamente al contador electrónico. Al mezclar la sangre en el vortex a la máxima velocidad posible por 1 ó 2 minutos se disuelven los agregados plaquetarios por completo en un 44 por ciento de las muestras y parcialmente en un 49 por ciento.