An improved method of detecting an enzyme in a sample, which enzyme is capable of adding or removing a chemical moiety to or from a nucleic acid molecule, thereby conferring the nucleic acid molecule with the ability to be extended to generate a novel detectable nucleic acid molecule, comprises the steps of allowing the sample to be tested for the presence of the enzyme to interact with the nucleic acid molecule; and testing for interaction of the enzyme with the nucleic acid molecule by detecting the novel nucleic acid molecule generated only in the presence of the enzyme. The preferred enzyme is a phosphatase. The methods have a number of applications, for example in enhancing the sensitivity of immunoassays, for detecting pathogen associated phosphatase, for diagnosing certain conditions and for detecting specific contaminants in a sample.