Correlation between blood inflammatory parameters and acute appendicitis (AA) remains controversial. This meta-analysis aims to evaluate whether platelet (PLT) indices including mean platelet volume (MPV), PLT count, and platelet distribution width (PDW) are associated with AA. Pubmed, Embase, and Cochrane Library databases were searched for observational studies published from inception through April 2020 by two independent investigators. Studies reporting associations between platelet indices and AA were selected for inclusion. Standardized mean difference (SMD) and 95% confidence interval (CI) were estimated for continuous outcomes using a DerSimonian-Laird random-effects model. Of 842 records identified, 17 studies with a total of 6793 subjects met our inclusion criteria. Meta-analysis indicated that compared with those in healthy controls, significant decrease in MPV levels was observed in subjects with AA (SMD - 0.34; 95% CI - 0.56 to - 0.12; P = 0.003). Subgroup analyses represented a significant reduction of MPV levels in patients aged ≥ 30 years and non-complicated/non-perforated AA. Due to the small number of studies and patients included in each subgroup, these subgroup analyses need to be interpreted with caution. However, none of the levels of PLT (SMD - 0.13; 95% CI - 0.28-0.012; P = 0.071) or PDW (SMD 0.30; 95% CI - 0.22-0.83; P = 0.257) was seen decrease or increase in subjects with AA. This meta-analysis indicates a significant decrease in MPV levels in patients with AA, which makes MPV have the potential of serving as a biomarker for AA. The associations of other PLT indices with AA need to be further examined.

BACKGROUND: Platelets, also called thrombocytes, are produced in bone marrow and are the second most numerous blood cells which circulate in blood and play a pivotal role in hemostasis, wound healing, angiogenesis. There is a large body of evidence that platelets are likely to contribute to inflammation in multiple diseases. Also, recent studies revealed the association between platelet indices (PI) and inflammation.
METHODS: PubMed, Scopus and Google Scholar databases were searched and only papers published in the last 10 years were consequently analyzed.
RESULTS: The most frequently evaluated parameters are mean platelet volume (MPV), platelet diversity index (PDW), plateletcrit (PCT) and the presence of larger platelets (P-LCRs platelet larger cell ratio). The values of platelet indices (PI) were elevated in patients suffering from type 2 diabetes mellitus, myocardial infarction, cancers or acute surgical conditions, such as appendicitis. The measurement of PIs does not generate additional costs and can be performed during routine cell blood count, not requiring additional blood samples.
CONCLUSIONS: Platelet indices may have prognostic and predictive value in numerous conditions.

Platelet indices (PI) -- plateletcrit, mean platelet volume (MPV) and platelet distribution width (PDW) -- are a group of derived platelet parameters obtained as a part of the automatic complete blood count. Emerging evidence suggests that PIs may have diagnostic and prognostic value in certain diseases. This study aimed to summarize the current scientific knowledge on the potential role of PIs as a diagnostic and prognostic marker in patients having emergency, non-traumatic abdominal surgery. In December 2015, we searched Medline/PubMed, Scopus and Google Scholar to identify all articles on PIs. Overall, considerable evidence suggests that PIs are altered with acute appendicitis. Although the role of PI in the differential diagnosis of acute abdomen remains uncertain, low MPV might be useful in acute appendicitis and acute mesenteric ischemia, with high MPV predicting poor prognosis in acute mesenteric ischemia. The current lack of consistency and technical standards in studies involving PIs should be regarded as a serious limitation to comparing these studies. Further large, multicentre prospective studies concurrently collecting data from different ethnicities and genders are needed before they can be used in routine clinical practice.