A preliminary study of factors influencing perception of menstrual blood loss volume.

Sixty-nine women with a convincing complaint of menorrhagia took part in a double-blind treatment trial. Menstrual blood loss was measured and the subject's own perception was carefully recorded. Only 38% had objective menorrhagia with a measured loss greater than 80 ml although 59% would qualify with an upper limit of normal of 60 ml. Overall the measured loss in the "heaviest" periods (69.6 +/- 7.3 ml; mean +/- SEM) were significantly greater than that of the "lightest" periods (42.7 +/- 4.7 ml; p less than 0.001), but there were many major errors in perception by individuals. Perceived daily blood loss volume on a 4-point rating scale gave the following group means and ranges: spotting, 2.5 ml (0.1 to 15.5); light, 5.7 ml (0.1 to 63.1); moderate, 16.1 ml (0.5 to 108.6); very heavy, 22.0 ml (1.4 to 215.8); very wide individual ranges of assessment are illustrated. As a whole the group was also able to distinguish between a day-to-day volume increase or decrease, but again there were many major errors. Some subjects who experienced a reduction in measured blood loss from one day to the next actually perceived this as a large increase. Menstrual pain and duration of bleeding were not found to influence perception of blood loss volume, whereas younger subjects (26 and under) were significantly more likely than older women (37 and over) to regard a moderate loss as very heavy. There was no significant correlation between the number of pads/tampons used and the measured menstrual loss, and some individuals showed extreme variations between blood loss and pad usage. This study suggests that the only reliable assessment of menstrual blood loss volume and changes in volume in women complaining of menorrhagia is obtained by objective measurement of blood loss by a technique such as alkaline hematin extraction.