Passive IAST tools provide only a sensor that attaches to the running application, usually induced by QA testing. Active IAST tools use DAST to activate IAST sensors but do not collate data from the two sources. True IAST tools like Invicti and Acunetix have actual interaction between the DAST scanner and the IAST sensor. The two communicate and influence each other to provide better test results, attain a very low false-positive rate, and fully confirm many security vulnerabilities.
Read more about the Invicti IAST solution.