Christopher Naugler - Lab Literacy for Canadian Doctors: A Guide to Ordering the Right Tests for Better Patient Care

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DR. CHRISTOPHER NAUGLER Abbreviations COPD chronic obstructive pulmonary disease

The diagnosis of most ear, nose, and throat ailments, and respiratory ailments, comes from a careful history and physical examination. Most presentations do not require laboratory testing. Keys to workup Diagnosis is based on the presence of compatible signs and symptoms, family history, pulmonary function testing, and response to treatment. Lab investigations Routine investigations are not recommended. Pearls Asthmatic individuals may have an elevated IgE, but this test is not useful in establishing a diagnosis.

Serum allergy testing is generally not useful, either: it delivers results with high false-positive and false-negative rates.

Keys to workup Findings from patient history and physical exam should guide decisions about testing. In the vast majority of cases, lab tests are not indicated. The exception is if you suspect a cough arises from another medical condition, such as heart disease. Base your decision about lab tests on their utility for diagnosing the suspected underlying disease. The key is to rule out life-threatening conditions (e.g., pneumonia, exacerbation of severe asthma or COPD, pulmonary embolus, heart failure).

Lab investigations Routine investigations are not recommended.

Keys to workup Diagnosis is clinical, based on the presence of compatible signs and symptoms. Lab investigations Routine investigations are not recommended. Keys to workup Diagnosis of acute bacterial rhinosinusitis is clinical, based on the presence of compatible signs and symptoms lasting more than 7 days. Lab investigations Routine investigations are not recommended. Pearls Routine nasal culture is not recommended.

If culture becomes necessary due to complications, obtain a specimen through maxillary tap or endoscopy.

Keys to workup Diagnosis is clinical, based on the presence of compatible signs and symptoms. Clinical scoring systems stratify patient risk for group A streptococcal infection (e.g., Centor score, McIsaac score). In the McIsaac score, each of the following scores a point: temperature higher than 38C (100.4F) absence of cough tender anterior cervical adenopathy tonsillar swelling or exudate patient age between 3 and 14 years Subtract a point for patients aged 45 years or older. Lab investigations Throat culture Order this if a patient: has a score of 2 or 3; initiate treatment if the culture is positive has a score of 4; culture and initiate treatment simultaneously For patients with a score of 0 or 1, routine throat culture is generally not necessary. Rapid antigen test This test has the advantage of providing a rapid answer, and most commercial kits have sensitivities in the range of 90% and specificities in the range of 95%.

The rapid antigen test is offered by some labs and also as a point-of-care test for office uses. Pearls A negative rapid antigen test does not need follow-up with a throat culture or tests for inflammatory markers.