Distribution of red blood cell indices in patients with α-thalassemia MDS (ATMDS) compared with a more general population with MDS. (A) MCV in ATMDS (n = 55) and MDS (n = 282) patients. Values are from the time of initial presentation with HbH or (if presentation data were unavailable) as close as possible to that time. Boxes enclose the 25th to 75th percentiles, and the middle bar denotes the median; vertical bars outline the 10th (bottom) to 90th (top) percentiles. (B) MCH in ATMDS and MDS. Boxes denote the same statistical distribution as in panel A. (C) Scattergram of MCV and MCH distribution in patients with ATMDS (○) versus MDS (•). (dashed lines) Eleven (23%) of 47 patients with ATMDS for whom MCH was available had MCH of 27 pg or greater, whereas 15 (27%) of 55 had MCV greater than 80 fL. In contrast, almost all MDS patients with MCH below 27 pg and MCV below 80 fL had evidence of acquired thalassemia. The non-ATMDS data source is personal communication from Drs Alison May, Graham Tennant, and Ala Al-Sabah (University Hospital of Wales in Cardiff; e-mail communication, January 19, 2004) regarding 282 nonthalassemic MDS patients; similar data were communicated by Dr David Oscier (Royal Bournemouth Hospital, Bournemouth, United Kingdom; oral communication to D.R.H. and Charles Craddock, Spring 1994) with respect to 101 MDS patients in Bournemouth and Southampton.