Platelet Counting: Ugly Traps and Good Advice. Proposals from the French-Speaking Cellular Hematology Group (GFHC)

Abstract

Despite the ongoing development of automated hematology analyzers to optimize complete blood count results, platelet count still suffers from pre-analytical or analytical pitfalls, including EDTA-induced pseudothrombocytopenia. Although most of these interferences are widely known, laboratory practices remain highly heterogeneous. In order to harmonize and standardize cellular hematology practices, the French-speaking Cellular Hematology Group (GFHC) wants to focus on interferences that could affect the platelet count and to detail the verification steps with minimal recommendations, taking into account the different technologies employed nowadays. The conclusions of the GFHC presented here met with a "strong professional agreement" and are explained with their rationale to define the course of actions, in case thrombocytopenia or thrombocytosis is detected. They are proposed as minimum recommendations to be used by each specialist in laboratory medicine who remains free to use more restrictive guidelines based on the patient's condition.

Reference Intervals for Platelet Counts in the Elderly: Results from the Prospective SENIORLAB Study

“…Sex- and age-independent platelet counts are still often employed in clinical medicine and are recommended [ 3 , 21 , 22 , 47 , 48 ]. Given the importance of the parameter in clinical medicine, this is somewhat interesting, as our study and others could identify sex- and age-specific differences [ 20 , 49 , 50 , 51 ].…”

“…Regarding platelet counts, there is no clear position on whether platelet count reference intervals should be age- and sex-specific. Whereas some authors propose stratification according to sex, age, or other characteristics [ 15 , 16 , 17 , 18 , 19 , 20 ], sex- and age-independent reference intervals are commonly used in clinical practice [ 21 , 22 , 23 , 24 , 25 ]. The importance of having accurate reference intervals for platelet counts available has been evident for a long time [ 26 ].…”

Effects of Time-Interval since Blood Draw and of Anticoagulation on Platelet Testing (Count, Indices and Impedance Aggregometry): A Systematic Study with Blood from Healthy Volunteers

“…Blood was smeared onto a glass slide and dried, and eventually colored using May-Grunwald-Giemsa stain. Isolated and clumped platelets were counted at the feather edge in ten adjacent fields using a Miller reticle [11]. We calculated the relative proportion of clumped platelets to the total number of platelets (sum of clumped and isolated ones).…”

“…Several parameters such as blood collection technique, processing, transport, storage conditions and duration can influence the results and contribute to increase both intra-and inter-laboratory variability [10]. One specific issue regarding platelets is their propensity to stick together in the collected blood sample, whatever the mechanism is-genuine aggregation or mere agglutination [11]; in the following text, we will use the word "clump" to remain purely descriptive. Clinical guidelines usually lack details on the suitable preanalytical conditions [7,12].…”

Pseudothrombocytopenia—A Review on Causes, Occurrence and Clinical Implications

“…(i) In vitro amikacin supplementation can prevent and dissociate platelet clumps due to EDTA, citrate [4], or heparin-PTCP [9] although controversially discussed [10]; (ii) Maintaining blood samples to 37 • C could lead to a more accurate platelet count (PC) or prevent EDTA-dependent PTCP [11,12]; (iii) A rapid analysis of EDTA blood specimen is advocated, due to time-dependent fall in PC from 1 min after blood collection to 4 h afterwards [4,12,13];…”