Below are a collection of excerpts from biomedical research articles. Excerpts are separated by newlines. Your task is to answer a question based these excerpts. Your response should be formatted as a `json` array.

For instance, given excerpts from articles studying breast cancer, and the question "what are some common genes associated with breast cancer?", an answer might be formatted like: ["BRCA1", "BRCA2", "TP53", ...]. Only include answers that are mentioned in the provided exerpts. The array should always have at least one answer; do not respond with an empty array []. Do not include any text in your response other than the answer array.

Context: In this study, macrocytic anemia due to FAD was defined as having an MCV ≥100 fL and folic acid ≤6 ng/mL; pernicious anemia as having MCV ≥100 fL, vitamin B12<200 pg/mL, and serum gastric parietal cell antibody positivity; iron deficiency anemia as having MCV<80 fL and iron<60 μg/dL; and thalassemia trait as having MCV<74 fL, red blood cell (RBC) count>5.0 × 10(12)/L, and Mentzer index (MCV/RBC)<13.
Complete blood count (CBC) parameters of 2196 certainly diagnosed (1272 beta-thalassaemia minor and 924 iron deficiency) samples were used to evaluate the following indices and formulas: Bessman index (RDW), Mentzer formula (MCV/RBC), England and Fraser formula (MCV - RBC - 5 x Hb- 3.4), Shine and Lal formula (MCV2 x MCH/100), Ehsani formula (MCV-10 x RBC), Srivastava formula (MCH/RBC), Green and King formula (MCV2 x RDW/Hb x 100), red distribution width index RDWI (RDW x MCV/RBC), RDW/RBC, as well as our formula (MCV-RBC -3 x Hb).
The ratio of the mean corpuscular volume (MCV) and red blood cell count (RBC) can be automatically calculated with any of the newer hematology analyzers.METHODS: The results of 398 patient screens were collected. Data from the set were divided into training and validation subsets. The Mentzer ratio was determined through a receiver operating characteristic (ROC) curve on the first subset, and screened for thalassemia using the second subset.
Mentzer ratio MCV/RBC detected all cases of beta thalassemia but was a poor index for iron deficiency detection.

Question:
What is included in the Mentzer index?
["mean corpuscular volume", "red blood cell count"]