Platelet Size Predicts Mortality in Patients with Sepsis

Researchers at Klinikum St. Georg (Leipzig, Germany) conducted a study involving 191 patients (median age 72, 38% women) with documented sepsis. The researchers prospectively evaluated MPV at admission, at the onset of sepsis, at the diagnosis of sepsis, and during the course of the disease, as a marker for the prediction of outcomes. These data were compared with data from 56 patients (median age was 74, 45.5% women) with acute upper and lower gastrointestinal (GI) bleeding, who served as control subjects. Data on other standard laboratory biomarkers and clinical parameters were collected at the same time.

The results showed MPV on admission and at the onset of symptoms was strongly associated with death. Of 183 sepsis patients, 41 (21.5%) that died had a higher MPV than survivors (9.6 vs. 9.19 femtoliter (fL), respectively). At the time of positive blood cultures, those values had increased (11.2 vs. 9.7 fL).

Parameters of temperature, leukocyte count, lactate, procalcitonin, and C-reactive protein (CRP) values, on the other hand, were not at all predictive of outcome. The researchers then determined that the best predictor of death or survival was when they used an MPV discriminatory value of 8.7 fL. The study was presented as poster session at the 15th International Congress on Infectious Diseases, held during June 2012 in Bangkok (Thailand).

“This figure is at the high end of the normal range of platelet volumes, but is still highly predictive of poor outcome, namely death, in patients with sepsis,” said lead author and study presenter Thomas Grünewald, MD, PhD, head of the division of infectious diseases and tropical medicine. “We saw that patients with MPVs higher than 8.7 are much more prone — the odds ratio is 3.2 — to worse outcomes (for example, death) than patients with MPVs lower than 8.7.”

MPV is a machine-calculated measurement of the average size of platelets found in blood and is typically included in blood tests as part of the CBC. Since the average platelet size is larger when the body is producing increased numbers of platelets, the MPV test results can be used to make inferences about platelet production in bone marrow or platelet destruction problems. A typical range of platelet volumes is 9.7–12.8 fL, equivalent to spheres 2.65 to 2.9 µm in diameter.

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