Abdus Salam Khan  ( Gandapur Basic Medical Science Faculty of Pharmacy, Distt. Head Quarter Hospital, D.I. Khan. )
Abdur Rahim Khan  ( Department of Chemistry (Biochemistry) and Distt. Head Quarter Hospital, D.I. Khan. )
Hayatuliah Khan  ( Department of Chemistry (Biochemistry) and Distt. Head Quarter Hospital, D.I. Khan. )

Urine of 30 pregnant females was tested for gravidex test. Both concentration and agglutination in­hibition (Beta monoclonal) tests were performed on the same urine specimens. Results showed that the sensitivity and specificity of the concentration (colour) test was much higher than that of the B monoclonal test (JPMA 39:1.31, 1989).

The laboratory confirmation of pregnancy has become a common and important laboratory procedure, especially in the diagnosis of ectopic pregnancies and in the management of tumours of placental tissue. Human chorionic gonadotropin (hCG) is a glycoprotein composed of two noncovalently lin­ked polypeptides the alpha and beta subunits. The individual subunits lack biological activity but be­come active when linked to form the intact com­plex. The alpha hCG subunit is essentially identical to the alpha chain of several other pit­uitarypolypeptide hormones like thyroid stimulat­ing hormone, follicle stimulating hormone and luteinizing hormones in their specific biological characteristics. Convenient immunologic proce­dures for the determination of hCG are available and are sensitive as well as specific. They are even more specific when they assay for the beta subunit of hCG. Various pregnancy tests are available, hav­ing different sensitivities and specificities. The time at which a given pregnancy testbecomes posi­tive also varies. The aim of the present study was to compare the sensitivity and specificity of recent­ly introduced concentration (colour pregnancy) test and B monoclonal slide test based on the prin­ciple of agglutination inhibition.

Thirty females whose ages ranged from 18 to 38 were included in the study. All had history of amenorrhoea varying from 3 days to S months. Urine of these females were tested for pregnancy. Both the concentration (colour) and slide (ag­glutination inhibition) tests were performed at the same time on the same specimen. The kits used were, Beta-monoclonal (1500) and HCG VIS­UAL ELISA TEST supplid by BGH biochemical company and Boehringer Manheim respectively.

The sensitivity and specificity of these pregnancy tests are shown in table I and II.

The slide and tube test use either agglutina­tion or agglutination inhibition as visible indicators of a colour as indication of a positive test¹.

As shown in table II there is a strong correla­tion between the results of colour test and B.monoclonal test except in three cases. In one case the subject has amenorrhoea of 3 days. At this stage the concentration of hCG in urine is very small, which cannot be detected by B.monoclonal test. However ELISA test is very sensitive to detect very small amounts (20-50 mu/ml) ². In a second case having amenorrhoea of 60 days, the colour test was positive while the B.monoclonal test was negative. In this case the ultrasound examination confirmed the pregnancy at a gestational age of 4 weeks. At a gestational age of 8 weeks the patients developed bleeding per vaginum and as a result the B.monoclonal test was negative. In a third case, the colour test was negative, while the B.mano­clonal test was positive. This positivity was most probably due to cross reactivity of luteinizing hor­mone with beta subunit of bCG. The same finding has been confirmed by other workers³. The preg­nancy was followed in all these cases for correla­tion of the results. From table lit is clear that, the concentra­tion test is more sensitive and specific than the B.monoclonal test. Similar findings have been re­ported by other workers⁴’. Although we have wor­ked on a small sample yet, we conclude that the concentration test, though little bit expensive, but its precision is much higher as compared to the B.monoclonal tests and other older tests used for diagnosis of pregnancy. Although Radioimmuno­assay technique (RIA) is the most sensitive and specific one, but it needs expensive equipment and the reagents are unstable (iodinated tracers). This property make them unsuitable for 24 hours stat pregnancy testing. So choosing method for stat pregnancy testing is no longer difficult and we recommend the use of concentration (VISUAL ELISA hCG TEST) test, in local hospitals.

The authors wish to thank M/s Muslim Scientific Traders 3 - Syed Moj Darya Road, Lahore for supplying the Kits.

1. Demers, L Pregnancy testing. Endocrinal. Metab. Coin. Educ. Frog (AACC), 1986; 4:1.
2. Birken, S., Canfield, R., Agosto. G. and Lewis. J. Preparation and Characterization of an improved beeta. COOH. terminal immunogen for generation of specific and sensitive antisera to human chorionic gonadotropin. Endocrinology, 1982; 110:1555.
3. Wenk, R.W. The perfect pregnancy test. Special topics No. ST 85-6 (ST-447), Check sample. Cont. Educ. Prog. (ASCP), 1985; 23:1.
4. Romero, It, Kadar, N., Copel, J.A., Jeanty, P., De Cher­ney, A.H., and Hobbins, J.C. The effect of different human chorionic gonadotropin assay sensitivity on scre­ening for ectopic prcgnancy. Am. J. Obstet. Gynecol., 1985; 153:72.