AJP - Heart and Circulatory Physiology, Vol 257, Issue 4 1306-H1311, Copyright © 1989 by American Physiological Society
An optical hemoglobinometer for whole blood
J. L. Schmalzel, J. M. Steinke, V. T. Randal and A. P. Shepherd
Department of Physiology, University of Texas Health Science Center, San Antonio 78284.
To overcome the disadvantages of the presently available hemoglobinometers,
we have developed an optical instrument that measures the total hemoglobin
(Hb) concentration in whole, undiluted blood. The device uses an infrared
light-emitting diode to illuminate a capillary tube filled with a sample of
whole blood. Light scattered in the blood travels a short distance down the
length of the capillary tube, passes through a second light path, and
reaches a photodetector, the output of which is amplified, digitized, and
fed into a microprocessor. The microprocessor computes the Hb concentration
as a nonlinear function of the light intensity. The optical device yielded
Hb content measurements that correlated well with standard methods (r =
0.99, slope = 0.94, mean absolute difference = 0.75 g Hb/dl). Thus the
accuracy appears to be less than 1 g Hb/dl. The advantages of the present
device are as follows: 1) no chemical reaction is required (hence neither
accurate dilutions nor toxic reagents are necessary); 2) it reads Hb
concentration within a few seconds; 3) it can be operated by unskilled
personnel; 4) it could be made portable and thus could be operated in the
field, in rural settings, or at accident sites; 5) sample size is small
(25-70 microliters); and 6) the same capillary tube can be centrifuged if a
measure of hematocrit is also desired. A detailed parts list and circuit
diagram are presented, and sources of error are discussed.
