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How the test works Unlike the traditional Clearblue Pregnancy test, the new Clearblue Digital Pregnancy Test with Conception Indicator contains two test strips, a low sensitivity strip and a high sensitivity strip. Inside a Clearblue Digital Pregnancy Test with Conception Indicator Urine travels up the Absorbent Sampler and flows through the pad. If hCG is present in the urine it will bind to anti-hCG antibodies attached to blue dye in the pad. The urine moves along both test trips. As the hCG and anti-hCG antibodies pass through the result line zone, they bind to anti-hCG antibodies to form blue result lines.
Both strips contain a result line; the low sensitivity strip also contains a control line. The Test monitors the control line on the low sensitivity strip and only when a valid control line has been detected will the result lines on both the strips be determined.
At low concentrations, hCG binds on the high sensitivity strip. At higher concentrations, hCG will also bind to the low sensitivity strip. The concentration of hCG detected in the results lines of the two strips determines the result of the Conception Indicator: 1-2 weeks since conception; 2-3 weeks since conception; 3+ weeks since conception. If no hCG is present, the anti-hCG antibodies attached to blue dye flow past the result zones on both strips, and no lines will be formed giving a Not Pregnant result. If insufficient hCG is present, result lines may form but will be below the lowest thresholds set, and a Not Pregnant result will be displayed.
The lines produced on the strips cannot be read by eye. Instead, an optical system is used to measure the density of the lines. A red light shines onto these specific areas, and the light reflected is converted into an electrical signal.