Assessment of Decision Support for Blood Test Ordering in Primary Care

The majority of general practitioners in the Netherlands have replaced traditional paper-based patient records with computer-based records; physicians enter patient data themselves in the computer during patient encounters (1). The use of electronic patient records creates new opportunities to influence physician behavior through implementation of decision support systems (2-7). In recent years, researchers have documented various computer-based decision support systems that have influenced physician behavior (8-17). Other investigators, however, have reported that computer-based decision support has not affected patient care (18). To resolve the issue, investigators have compared the results of studies that were conducted in different settings, used different methods, and involved different populations (19). Studies comparing different methods of providing computer-based decision support in randomized trials are not available. In the Netherlands, 3% to 4% of patient encounters with general practitioners in primary care result in the ordering of blood tests (20). However, ordering of blood tests is not always appropriate (21-29). Researchers argue that excessive ordering of tests causes physicians to pursue evaluation of false-positive results, which in turn leads to additional unnecessary diagnostic examinations (30-35). Two methods have proven effective in reducing the number of tests ordered by Dutch general practitioners. The first method is based on restricting the number of tests that are listed on an order form. Zaat and colleagues (36, 37) developed a restricted paper order form that replaced the existing form. The second method involves introduction of indication-oriented order forms that are based on clinical practice guidelines (38-40). We hypothesized that an indication-oriented order form based on guidelines, which would provide an optimally restricted list of tests that are relevant for a specific indication, would be more effective in decreasing the number of tests ordered compared with an order form that provides an initially limited list of tests. We therefore conducted a randomized trial to compare the effect of two versions of BloodLink, a computer-based clinical decision support system, on blood test ordering among Dutch general practitioners. Methods Participants In August and September 1995, all 64 practices (94 general practitioners) in the region of Delft, the Netherlands, were invited to participate in the study. Only practices that had replaced their paper-based patient records with electronic records and were using the computer during patient encounters were eligible. A total of 46 practices (62 general practitioners) agreed to participate. Randomization To avoid contamination, we performed random allocation at the level of the practice (41, 42). The practices were first stratified by type: solo practices or group practices (two or more general practitioners in the same practice). Each practice was subsequently assigned by simple random allocation to use BloodLink-Restricted or BloodLink-Guideline for the full study period. A researcher who was not involved in the study and was blinded to the identity of the practices performed the randomization by using a random-numbers table. After randomization, 22 practices involving 30 general practitioners were assigned to use BloodLink-Restricted and 24 practices involving 32 general practitioners were assigned to use BloodLink-Guideline. Intervention We developed two versions of BloodLink, a computer-based decision support system. BloodLink-Restricted initially displays a reduced list of tests, whereas BloodLink-Guideline is based on the guidelines of the Dutch College of General Practitioners. Both versions of BloodLink are integrated with the computer-based patient record (43). The option to use BloodLink was added to the screen that the general practitioner uses when entering data in the electronic patient record during patient encounters. The general practitioner can activate BloodLink to order blood tests as an alternative to using paper order forms. Because the total number of tests that can be ordered is too large to display on a computer screen, a set of tests is presented for selection. If the physician requires additional tests that are not currently displayed, he or she can type the first few letters of the names of the required tests, and the system will present all possible matches (including those corresponding to possible typing errors of the general practitioner) for selection. The number of tests that the general practitioners had at their disposal was the same both before and during the intervention (52 clinical chemistry tests and 46 microbiological tests). Options for specific instructions to the laboratory (for example, urgent processing or fasting values) are available. Once the physician has made his or her selections, BloodLink prints a patient-specific test order form and instructions for the laboratory and updates the patient record with the tests that have been ordered. The only difference between the two versions of BloodLink is the method used to present the initial set of tests to the general practitioner. BloodLink-Restricted is based on the idea of a restricted order form. It offers the general practitioner an initial set of 15 tests that have been shown to cover most of the clinical situations seen in primary care (36). BloodLink-Restricted can be viewed as a general electronic order form that presents only 15 tests on the screen, together with a field labeled other tests that allows the physician to request any other blood test (43). The 15 tests are alanine aminotransferase, aspartate aminotransferase, total bilirubin, cholesterol, creatinine, erythrocyte sedimentation rate, free thyroxine, -glutamyltransferase, glucose (and fasting glucose), glycosylated hemoglobin, hemoglobin, mean corpuscular volume, PaulBunnell, potassium, and thyroid-stimulating hormone. At any time, the physician can customize tests for individual patients by adding or deleting tests. BloodLink-Guideline is based on the guidelines of the Dutch College of General Practitioners. By January 1996, the Dutch College of General Practitioners had published 54 guidelines. Some guidelines focus on symptoms that are frequently seen in the primary care setting, such as acute diarrhea, acute sore throat, low back pain, alcohol abuse, fever in children, and sleeping disorders. Other guidelines focus on common diseases in primary care, such as diabetes, asthma, depression, dementia, and eczema. Finally, a set of guidelines covers preventive medicine. We reviewed the most recent version of each guideline, available in January 1996, and noted whether it contained a reference to a blood test (44). We determined the clinical situation in which the test should be performed (indication) and the tests that should be performed in that situation (advised tests). When general practitioners activate the system, BloodLink-Guideline first provides an overview of the available guidelines. The names of these guidelines are familiar to Dutch general practitioners. The general practitioner selects the appropriate guideline. A guideline may describe several different indications for requesting blood tests; for example, the guideline for blood tests and liver disease mentions 10 different indications. After the indication has been identified, the system proposes the relevant tests. The general practitioner then decides whether to adhere to the protocol. At any time, the physician can customize tests for individual patients by adding or removing tests from the proposed list. Although new guidelines are published at regular intervals, the currently available guidelines cover only a limited set of indications for blood tests (44). In the absence of national guidelines, local or regional guidelines may be used. The version of BloodLink-Guideline used during the clinical trial in the Delft region included three regional guidelines for anemia, AIDS, and clotting disorders, in addition to all national guidelines. Even with these additional guidelines, BloodLink-Guideline does not cover all possible indications for blood tests in primary care. To deal with these situations, the general practitioner can select the heading other indication and order any test. Protocol Before the study, the general practitioners were using two paper order forms: one for clinical chemistry and one for microbiology. After BloodLink was installed, one of the authors gave a brief orientation presentation to the participating practitioners. During a 3-month phase-in period, the general practitioners were allowed to use BloodLink in their practices to become acquainted with the system. After this period, the general practitioners were asked whether they were willing to participate in the trial. The study period was March 1996 through February 1997. Physicians always had the choice to use either the BloodLink software or the paper forms to order clinical chemistry and microbiology tests; thus, paper order forms were still available during the entire intervention period. When the general practitioner ordered blood tests during a patient encounter, only one order form was generated regardless of whether the general practitioner used paper forms or BloodLink. The electronic patient record monitored use of BloodLink by the practitioners. To include the requests for blood tests that were made by using traditional paper forms, we retrieved from the regional laboratory all requests for blood tests. Outcomes We counted the number of order forms that the laboratory received from the general practitioners and the number of tests on each form. The main outcome measure was the average number of tests per order form (including paper forms) per practice (summary variable). We defined the most frequently ordered tests as the tests that accounted for 80% of the total number of tests ordered. For these tests, we compu