The invention relates to a method and test kit for quantitative determination of the amounts or relative proportions of polynucleotides in a mixture. The invention enables assessment of dynamic variations in a mixed population of organisms using affinity aided solution hybridization. The test kit comprises organized pools of polynucleotide probes having approximately the same number of nucleotides, which are distinguishable using resolution enabling tags providing the probes with different sizes. The resolution enabling tags may simultaneously act as tracer, affinity or primer tags. The probes are allowed to hybridize with affinity tagged analyte polynucleotides. The result is hybrids, recoverable on separation aiding tools provided with counterparts of the affinity tag. After the quantitative release of the probes, the individual probes can be amplified and recorded. The method and test kit are useful for determining hygienic and epidemiologic situations and evaluating the effect of antibiotic treatment and sanitary measures.