Physiological Measurements NEW APPROACH TO HAEMOGLOBINOMETRY BASED ON REFLECTANCE PHOTOMETRY

This paper describes a new approach to haemoglobinometry based on reflectance photometry using pretreated cell strip. A disposable cell strip is designed to absorb standardised volume of blood from a finger prick without any volumetric measuring apparatus. Pretreatment of the cell oxidises haemoglobin to methaemoglobin, thereby eliminating the errors of Tallqvist's method. The behavior of blood cells on chemically treated as well as untreated filter paper is studied by scanning electron microscopy. The principle behind the proposed method is used to fabricate a small, cheap and portable haemoglobinometer using LED's and suitable sensors. This technique provides a simple and reliable means of ascertaining haemoglobin content in blood for routine as well as field use. INTRODUCTION Haemoglobin percentage in blood is a diagnostic parameter for knowing different kind of anaemia. The conventional clinical methods [l,2] are cumbersome for field use. This is because these techniques involve diluting fluids, pipettes and use of standards. Further; fairly long time is required for a chemical reaction to be completed. The optical wedge method [33 and Tallqvist's filter paper technique L43 are of little clinical use as the colour matching gives erratic results. In this paper, experimental investigations leading to the development of haemoglobinometer based on reflectance photometry using chemically pretreated filter paper are presented. The scanning electron microscopy is used to study the behavior of blood cells. The choice of chemical used is confirmed by spectroscopic studies. In addition, colorimetric estimation using 640 nm filter is also presented. EXPERIMENTAL INVESTIGATIONS Blood samples Blood samples for this study were routinely obtained from the clinical chemistry laboratory. Specimens were collected by venipuncture into EDTA, containing evacuated blood collection tubes and kept at 4 degree cent. before and during transport to the lab. within 24 hrs. of collection. Further, capillary blood samples were obtained by finger prick with a spring loaded sterile lancet, Colorimetric estimation To 0.02 ml of blood was added 4 ml of N/10 HC1 and 0.1% NaN02 separately. Brownish red colour so obtained showed gradual increase in optical density with an increase in Hb content as shown in Table I.