The present invention includes methods and devices for preventing interfering substances from affecting the accuracy of a lateral flow immunoassay. In preferred embodiments, a test strip includes a capturing zone that includes at least one mobile capturing reagent that separates at least one interfering substance from the analyte. The capturing zone is preferably located upstream of the sample application zone. In some embodiments, the reagent/conjugate zone is also located upstream of the sample application zone. The capturing zone may be located upstream, downstream, or overlapping with the reagent/conjugate zone in these embodiments. In other preferred embodiments, one or more mobile capturing reagents are included in the elution medium/running buffer. In yet other embodiments, the capturing reagent is incorporated into a sample collection device of a sample collection system, preferably separate from the chromatographic test strip. A lysis zone is also included in some preferred embodiments.