Infectious disease is a specialty that distinguishes itself by many unique features. The recognition of new diseases or the etiology of old diseases is unparalleled among specialties. The application of molecular diagnostic testing supports establishing the etiology for many of these new entities. The proliferation of new antimicrobial agents is occurring at a rate to meet clinical needs with some recognized deficiencies. The aspect of this specialty that has remained stable over decades has been the reliance of the infectious disease specialist on his or her most valued diagnostic test, medical semiology. The careful gathering and interpretation of data from interviewing and examining patients are critical to our clinical success. In this issue of the journal, Sexton et al1 emphasize the importance of this invaluable tool in diagnosing and managing infectious diseases. The authors emphasize the role of this tool in rules 4, 5, 8, 16, and 17. The consequences of an incomplete history and physical examination can lead to a failure to correctly diagnose or manage the patient's illness.
A recent patient presented to our hospital with abdominal pain, diarrhea, cor pulmonale, and numerous comorbidities including hypertension, diabetes, and chronic obstructive pulmonary disease. The patient's ethnic origin and travel history were incomplete. Only after a careful review of her earlier outpatient visits did we discover that the patient was of Filipino ethnicity, explaining her risk for Schistosoma japonicum, which was found at autopsy causing fibrosis in her lungs and liver. A careful review of these elements of history could have led to an earlier diagnostic consideration of this entity.
Unfortunately, clinicians rely on imaging services and laboratory tests far more frequently than a carefully executed history and physical examination for establishing a diagnosis or monitoring a therapeutic response. Young clinicians are too often willing to perform computerized tomography or magnetic resonance imaging studies of the brain before conducting a funduscopic examination to determine whether the optic disc margins are blurred or whether spontaneous venous pulsations are reduced as early signs of intracranial hypertension. The reliance on imaging has been associated with false negative tests resulting in the clinician being steered away from the appropriate diagnosis.
A close colleague of mine always challenges medical students and residents to ask why (rule 17) with any diagnosis so that when the "pieces don't fit you shouldn't quit." Reliance on another person's inadequate diagnosis results in you getting credited for an incorrect diagnosis (rule 14).
The use of a response to therapy is, as appropriately pointed out by the authors, a potential misleading cue. "Post hoc, ergo propter hoc" is the principle where "after this, therefore because of this," where if one event happens after another, then the first must be the cause of the second. The patient got better when therapy is started; therefore, the improvement is caused by the therapy. One such example would be a patient improving after receiving antibiotics when the diagnosis is a viral respiratory tract infection. This is an obvious example of therapy misguiding our impression that the disease is responding to the intervention (rule 28).
The authors have shared their insight from years of experience as infectious disease specialists, establishing clinical rules that they have learned from treating numerous patients.
Two additional rules could be added: rule 31-the newest agent is not always needed nor is it the best therapy. We are amazed every time we ask a group of clinicians about the frequency of penicillin resistance among group A streptococci. Young clinicians often answer with some figure when there has never been a documented case of Streptococcus pyogenes resistant to penicillin ever reported.2 Nonetheless, many new agents have been approved for the treatment of group A streptococcal pharyngitis that are more costly, with results that are not superior to penicillin. Indeed, for some drugs, such as the macrolides, group A streptococcal resistance has been problematic.
Another suggested new rule would be rule 32-basic principles of management that are relatively inexpensive need to be incorporated in the management of the patient, and more expensive newer therapies are not always better. In the management of sepsis, early goal-directed therapy (saline), glycemic control, and appropriate antibiotic use are all superior to activated protein C, with a greater risk reduction in mortality.3-6
We are indebted to Sexton et al for reminding us of some very basic rules that infectious disease clinicians need to pass on to their fellows, residents, and students, who in turn, will augment and pass on to their students. In an era where we have molecular biology to thank and imaging services to augment our patient care, we need to remember that these rules compliment our approach and not replace them.
1. Sexton DJ, McDonald M, Spelman D, et al. Thirty operating rules for infectious diseases apprentices. Infect Dis Clin Pract
. 2007;15(2): 100-103.
2. Fakih MG, Hilu RC, Savoy-Moore RT, et al. Do resident physicians use antibiotics appropriately in treating upper respiratory infections? A survey of 11 programs. Clin Infect Dis
3. Rivers E, Nguyen B, Havstand S, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med
4. Ibrahim EH, Sherman G, Ward S, et al. The influence of inadequate antimicrobial treatment on blood stream infections on patient outcomes in the ICU setting. Chest
5. Vanden Berghe G, Wonters P, Weckers F, et al. Intensive insulin therapy in critically ill patients. N Engl J Med
6. Bernard GR, Vincent JL, Laterre PF, et al. Efficacy and safety of recombinant human activated protein C for severe sepsis. N Engl J Med