The value of cervical cytology in diagnosing early invasive carcinoma and preinvasive carcinoma-in-situ lesions of the uterine cervix is well established, and its practical application as a screening test has been demonstrated among patients attending hospital (Yule and Cameron, 1961), local authority (Jones and Metcalfe Brown, 1965), and general practice clinics (Macgregor and Baird, 1963). Long-term screening programmes among wider communities (Boyes et al., 1962 ;Bryans et al., 1964) have been associated with reported falls in the incidence of invasive cervical carcinoma in the screened population, and, while follow-up data from these long-term programmes remain limited, their accumulating experience may shortly allow a firme. assessment of whether they can achieve their ultimate aim, a major reduction in mortality. To date no screening programme has been shown to have this effect.In this country professional opinion and public demand have combined to stimulate a recent increase in cytological services; a nation-wide service has been advocated, but a shortage of cytologists and technicians has made progress toward this end slow (British Medical 7ournal, 1965). In an assessment of the practical implications of screening all women over 20 years, with repeat examinations every five years, it has been estimated (Wilson, 1965) that, for a population unit of 250,000 (roughly the size served by a group laboratory), a service on this scale would mean screening one-fifth of the 83,000 women over 20 each year-that is, about 17,000 a year. Expanded to the country as a whole such estimates indicate a screening load likely to overwhelm available cytological services, and this gap between demand and available resources for cervical screening has been a factor adding impetus to the search for possible alternatives to cytology.One development in recent years has been the introduction of a biochemical test that promised to be very much easier to apply and much cheaper to carry out on a mass scale. Chayen et al. (1962) showed that 6-phosphogluconate dehydrogenase was extremely active in several types of malignant tumour and that the presence of this enzyme could be recognized histochemically. Bonham and Gibbs (1962) MethodsThe study was carried out among women attending (a) the outpatient department at University College Hospital Obstetric Hospital and (b) cervical screening clinics held in the surgeries of four local practices. Married hospital patients aged 20-65 became eligible for inclusion on making a first attendance at one or other of the hospital's antenatal, gynaecology, or cancerdetection clinics. Non-hospital patients entered the survey on acceptance of appointments for cervical screening offered to all married women aged 20-65 on the practice lists. At both hospital and practice clinics specimens for 6-phosphogluconate dehydrogenase enzyme estimations and cytological examination were obtained from each patient during a single clinic attendance. Cytological examinations and enzyme estimations were carried out at U...
SYNOPSISThe effect of blood in vaginal fluid on the assay of 6-phosphogluconate dehydrogenase has been studied. Alternative assay procedures have been investigated to overcome these effects.A study of the activity of 6-phosphogluconate dehydrogenase (Enzyme Commission No. 1.1.1.44) in the vaginal fluid of large numbers of women has been carried out to investigate whether the assay of this enzyme would be suitable for widespread application as a screening procedure for early gynaecological cancer (Bonham and Gibbs, 1962;Labrum, 1965;Cameron, 1964; Nerdrum, 1964;Boyd, Gibbs, Labrum, and Philps, 1967).Many specimens of vaginal fluid contain apprecible amounts of blood, although specimens are not taken during menstruation. This is particularly so with specimens from patients with carcinoma of the cervix. During the course of these studies we have observed that blood interferes with the assay used for 6-phosphogluconate dehydrogenase which is based on a final measurement of the extinction at 340 m,u due to NADPH2. Lowry, Passonneau, and Rock (1961) have reported that blood, even at very low concentrations, was capable of greatly accelerating NADH2 and NADPH2 oxidation at pH values from 8 to 12. As the enzyme test described by Bonham and Gibbs (1962) takes place at pH 9 0 considerable reoxidation of the nucleotide may well take place in this test system due to the presence of significant amounts of blood.This paper deals with the investigation of this problem and describes a method of overcoming it by the addition of tryptophane and nicotinamide to the assay system to inhibit both enzymic and nonenzymic destruction of the nucleotides.To overcome the difficulty caused by reoxidation of NADPH2 due to the presence of blood, the reduced nucleotide was coupled non-enzymically to cause a reduction of a blue dye (2-6 dichlorophenol indophenol). Thus the reduction can be measured by following the bleaching of the dye at 600 m,u. 189 METHODSVaginal fluid was collected from patients with carcinoma of the cervix in the manner described by Bonham and Gibbs (1962). This source of fluid was chosen to guarantee an active sample. The amount of blood present was determined by the following modification of the method of Meijer (1962).Specimens of vaginal fluid were made up to 3 ml. with glass-distilled water and then homogenized using a Teflon pestle in a glass barrel. To 1 ml. of the homogenate 0 15 ml. of 0,14 M ammonia solution was added and the volume made up to 3 ml. After standing for 10 minutes, the sample was centrifuged and the extinctions read at 580, 605, and 630 m,u.Whole blood (obtained by venepuncture) from the same patient, 0-02 ml. plus 0 15 ml. of 0-14 M ammonia solution, was made up to 3 ml. with glass-distilled water and the extinctions were read at 580 and 605 mit.The percentage blood in the specimens was calculated as follows: % blood in specimen = (Es8o -E605) -(E605 -E630) sample x 2 (E5E0 -E*05) whole bloodThe values were expressed as a percentage of whole blood on the basis of a normal haematocrit value. Bl...
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