Effectiveness of a Laboratory Gate-Keeping Strategy to Overcome Inappropriate Test Utilization for the Diagnosis of Heparin-Induced Thrombocytopenia.

The purpose of medical laboratories is to provide analyses from blood and other specimens to aid diagnosis and treatment. The analytical spectrum provided by laboratories all over the world has expanded continuously over the past decades. The increasing availability of tests with fast turnaround times combined with defensive medicine strategies has led to an overuse of laboratory diagnostics.1–3Health care expenditures, in turn, increase every year. In Austria, for example, respective per capita expenses related to healthcare increased from $2,249 USD in 1995 to $5,038 USD in 2014 (9.5–11.2% of gross domestic product, respectively).4 Although in vitro diagnostic (IVD) expenses contribute only approximately 0.8% to these numbers,5 laboratories have to find strategies to overcome inappropriate test utilization, particularly because an overuse of laboratory diagnostics might even be harmful to patients.6 Such strategies include educational interventions,7 laboratory diagnostic pathways,8 minimum retesting intervals,9 and reimbursement or funding models amongst others. Themodelwe describe here is a gatekeeping strategy. We chose laboratory diagnostics for detecting heparin-induced thrombocytopenia (HIT) type II, a prothrombotic immune response to heparin treatment, potentially leading to life-threatening conditions,10 whose diagnostic challenges have also been recently highlighted in this journal.11 Detection of anti-PF4/heparin antibodies (HITAb) during the disease can be performed either using functional methods, such as platelet aggregation procedures or serotonin releasing tests, or using immunoassays.12,13 In the department of laboratory medicine of the Paracelsus Medical University (Salzburg, Austria), only the latter type of test is provided. This test was chosen for a gate-keeping strategy because respective test ordering is done quite often as comparedwith the much lower and predictable frequency of HIT, ranging from 0.3 to 3%, depending on the patient collective and the type of heparin used.12,14 Prior to antibody testing, pretest probability can be estimated using a scoring system, commonly known as the 4Ts, consisting of four questions, eachwith three possible answers. Each answer reflects 0, 1, or 2 scoring points. A total of 3 points is associated with a negative predictive value (NPV) of 99.8% for the presence of HIT regardless of the party responsible for scoring or prevalence of HIT.15 Based on this evidence, we implemented the respective questions into our physician order/entry system, providing answer options as separate dropdown menus. Answering all the questions was made mandatory prior to HIT-Ab test ordering. The answers were automatically translated into the respective point values and summed. This informationwas then transferred into the laboratory information system (LIS). In test orderswith a value 3, the orderwas heldupandtheclinicianwas informed that theprobabilityofa positive HIT-Ab test in the patient was <2%. The clinicianwas also asked to call the laboratory if he/she still wished the analysis to be performed regardless of the scoring value. Implementation was done in accordance with the interdisciplinary coagulationworking groupof thehospital, comprising representatives from five clinics, the department of laboratory medicine, and the pharmacy. Internal medicine coagulation consultative clinicians were directly informed about the date of implementation and all other departments were informed using the hospital intranet. Testing was performed using the ID-Particle Gel Immuno Assay (PaGIA) Heparin/PF4 Antibody Test (Bio-Rad Laboratories, Hercules, CA). Letter to the Editor