Diagnosis: Clinical Scenario
Typhoid fever is one of the prevalent disease conditions in a developing countries like the Philippines. In 1996, the Department of Health has reported an increase in morbidity and mortality secondary to typhoid fever. At present, the initial diagnosis is largely dependent on clinical presentation. Although, many consider blood culture as the gold standard for diagnosis, the results are not readily available (earliest is 3 days after specimen collection), and its appropriateness as the reference standard is questioned. In addition, the cost is prohibitive for many patients. The Typhidot test, developed by a Malaysian scientist for the rapid diagnosis of typhoid fever has recently been introduced and made commercially available. This test utilizes the principle of antigen-antibody reaction. It costs less than the blood culture, and results are supposed to be obtained within the day of the examination. However, variations exist with regards to conduct of this test. Not all hospital laboratories perform Typhidot test on a daily basis, i.e., there are specified days for which specimens submitted for this test are accumulated and the test is done only during such days. Thus, results will be delayed for specimens submitted on days not coinciding with such schedules.
A 40-year old female is admitted in a nearby hospital due to high grade fever for the past 5 days. Aside from anorexia and body malaise, she denies any other symptoms. At the emergency room she appeared to be dehydrated. Otherwise, all other physical examination findings were essentially normal. The initial diagnosis is enteric fever. Other disease conditions being considered are systemic viral infection, urinary tract infection and dengue fever. The resident-on-duty requested for a CBC, urinalysis, blood culture and a typhidot test. No antibiotics were started during this time. Results of the CBC and urinalysis are unremarkable. The results of the typhidot test are positive for IgM , and negative for IgG . The resident calls you at your clinic asking for help regarding interpretation of these test results. Together you pose the question, 'in a patient with suspected typhoid fever, what is the accuracy of the Typhidot test for making the diagnosis?' You advise her to do a search of the local literature using Herdin, a local database, and she successfully tracks and retrieves a recent article by Collantes & Velmonte on the accuracy of Typhidot test in the diagnosis of typhoid fever. (Phil J of Med - Infectious Dis 1997; 26:61-63.)
Read the article and decide:
- Are the results of this diagnostic article valid?
- Are the valid results of this diagnostic study important?
- Can you apply this valid, important evidence about a diagnostic test in caring for your patient?