Iconic Colorimetric Test Device with Reduced Susceptibility To False Positive and False Negative Readings

Abstract

Laminated test devices in which positive results are detected by the appearance of a symbol on the surface of the device due to a color change in an indicator in the device are improved by placing the indicator lamina on one side of a light-transmissive substrate sheet and a pigment lamina on the other side, the indicator lamina forming the icon and the pigment lamina forming the background, the pigment being the color of the indicator prior to the color change. This arrangement reduces false positive readings by obscuring the outlines of the symbol prior to the color change. False negative readings are reduced by further changes in the arrangement of the laminae.

1 . A method for the identification of a condition indicative of bacterial vaginosis in a patient by analyzing a sample of vaginal fluid from said patient, said method comprising applying said sample to a solid alkali and a gas-permeable indicator lamina of material permeable to gas but impermeable to aqueous liquids, said gas-permeable indicator lamina impregnated with an indicator that undergoes a detectable transition upon contact with amines, the penetration of said amines into said gas-permeable indicator lamina correlating, without also analyzing the pH of said sample or analyzing said sample for the presence of clue cells, to bacterial vaginosis.  
     
     
         2 . The method of  claim 1  wherein said indicator is a visual indicator that changes color upon contact with gaseous amines.  
     
     
         3 . The method of  claim 1  wherein said indicator is bromocresol green.  
     
     
         4 . The method of  claim 1  wherein said solid alkali is a member selected from the group consisting of alkali and alkaline earth metal aluminates, carbonates, and hydroxides.  
     
     
         5 . The method of  claim 1  wherein said solid alkali is a member selected from the group consisting of sodium aluminate, sodium carbonate, and magnesium hydroxide.  
     
     
         6 . The method of  claim 1  wherein said material permeable to gas but impermeable to aqueous liquids is ethyl cellulose.