A diagnostic tool is disclosed for accurately and rapidly diagnosing the condition of an ailing organ. Although applicable to numerous organ and organ systems, this application particularly illustrates the concept of conjunctive marker utilization as it relates to diagnosing and distinguishing congestive heart failure. The invention particularly relates to the conjunctive utilization of cardiac Troponin I (cTn-I) and natriuretic peptide, e.g. ANP, pro-ANP, BNP, pro-BNP and CNP as a retrospective tool for diagnosing the underlying mechanism of heart failure and as a prospective analytical device for monitoring disease progression and efficacy of therapeutic agents.