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The Mentzer index, described in 1973 by William C. Mentzer, [1] is the MCV divided by the RBC count. It is said to be helpful in differentiating iron deficiency anemia from beta thalassemia trait. [2] [3] The index is calculated from the results of a complete blood count.
Red blood cell distribution width (RDW or RDW-CV or RCDW and RDW-SD) is a measure of the range of variation of red blood cell (RBC) volume, yielding clues about morphology. [ citation needed ] Erythropoietic precursor indices
RDW-SD is calculated as the width (in fL) of the RBC size distribution histogram at the 20% height level. This parameter is, therefore, not influenced by the average RBC size (mean corpuscular volume, MCV). [7] RDW-CV (expressed in %) is calculated with the following formula: RDW-CV = (1 standard deviation of RBC volume ÷ MCV) × 100%. [8]
The most common causes of microcytic anemia are iron deficiency (due to inadequate dietary intake, gastrointestinal blood loss, or menstrual blood loss), thalassemia, sideroblastic anemia or chronic disease.
The rationale for the diagnostic odds ratio is that it is a single indicator of test performance (like accuracy and Youden's J statistic) but which is independent of prevalence (unlike accuracy) and is presented as an odds ratio, which is familiar to medical practitioners. [citation needed]
Secondary polycythemia is considered to be more common, but its exact prevalence is unknown. [30] In one study using the NHANES dataset, the prevalence of unexplained erythrocytosis is 35.1 per 100,000, and was higher among males and among individuals between ages 50–59 and 60–69.
There are other names for the hematocrit, such as packed cell volume (PCV), volume of packed red cells (VPRC), or erythrocyte volume fraction (EVF). The term hematocrit (or haematocrit in British English) comes from the Ancient Greek words haima (αἷμα, "blood") and kritēs (κριτής, "judge"), and hematocrit means "to separate blood".
In fact, post-test probability, as estimated from the likelihood ratio and pre-test probability, is generally more accurate than if estimated from the positive predictive value of the test, if the tested individual has a different pre-test probability than what is the prevalence of that condition in the population.