On June 27th, the name of the current order “Respiratory (non-sputum) Culture without Gram stain” will change to “Throat Culture Comprehensive.” All other specimen collection details and culture workup will remain the same. Given the fact that there are currently several similarly named tests, this change is being made to reduce confusion regarding test selection and to clarify acceptable specimen types.
The majority of acute pharyngitis cases are caused by viruses, however, throat culture may aid in the diagnosis of bacterial pathogens. Particularly in pediatric patients, it is principally important to rule out group A Streptococcus (GAS; Streptococcus pyogenes) as the cause of pharyngitis. Clinical criteria (patient age, cervical adenopathy, fever, lack of cough, etc) can help guide appropriate testing for GAS which includes rapid antigen testing with reflexive culture when negative. The prompt diagnosis and treatment of streptococcal pharyngitis can help to speed the resolution of symptoms, reduce incidence of contagious transmission, and reduce the risk of suppurative (peritonsillar abscess, cervical lymphadenitis) and nonsuppurative (acute rheumatic fever and glomerulonephritis) complications. The majority of patients with negative antigen and/or culture results for GAS will experience resolution of pharyngitis symptoms without the need for additional testing or intervention.
In some circumstances, a provider may request a culture for non-GAS organisms that can be associated with pharyngitis. The “Throat Culture Comprehensive” order may be used to identify the following organisms, especially when isolated in predominant amounts as compared to the normal upper respiratory flora: β-hemolytic Streptococcus (Groups A, C, and G), Moraxella catarrhalis, Haemophilus influenzae, Arcanobacterium haemolyticum, Cryptococcus neoformans, and Streptococcus pneumoniae. Corynebacterium diphtheriae requires specialized growth media, and can be cultured by request as a send-out to the Michigan Department of Health and Human Services (MDHHS). Similarly, the “Throat Culture Comprehensive” order is not able to recover Fusobacterium necrophorum from throat swabs due to its anaerobic growth requirements.
Questions, comments and inquiries about this test may be directed to Dr. Adam Caulfield using the “contact us” link above.