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Sore ThroatJason Theiling, MD and Alison S. Clay, MD2/10/2015Objectives:Identify Red Flags for Sore ThroatPropose a Differential Diagnosis for Sore throat, including key features for various conditionsUse Clinical Decision Rules to determine who should receive testing for Strep ThroatSuggest Treatment Options for patients with Sore ThroatCompare and contrast the following patient histories, identifying key signs for your differential diagnosis: (note key findings are highlighted in yellow)32 year old patient presents with sudden onset of sore throat, fever, and headache 2 days ago. He has also noticed some swollen lymph nodes and is feeling quite tired. He does not have a cough.65 year old patient with significant past medical history presents with a 3 month history of hoarseness. The patient’s wife noticed a raspy voice a few months ago. He also notes that he has cough, which he attributes to his smoking. He has no other real complaints, except that he has noticed that his clothes are becoming a little loose.45 year old patient presents with sudden onset of fever, ear pain, and sore throat on the right side. The patient has also noticed some difficulty with swallowing and some difficulty speaking.What Diagnoses do you not want to miss? What are their key findings on history and physical?ConditionSigns and SymptomsEpiglottitis Severity out of proportion to exam Drooling and or Inability to swallow Muffled Voice/Inability to speak Peritonsillar AbscessUnilateral sore throat (1 point)Hot potato voice (1 point)Trismus (spasm of pterygoid muscles) (1 point)Retropharyngeal AbscessMay have had penetrating trauma (1 point)Difficulty swallowing or breathing (1 point)Submandibular infection Stiff Neck (1 point)Drooling and or Inability to swallow (1 point)Muffled Voice/Inability to speak (1 point)Crepitus along jugular vein (1 point)CancerUsually has a history of smokerChronic DurationHoarseness ConditionDiagnostic testing/(FILMS OR EXAM)EpiglottitisPeritonsillar AbscessSubmandibular Abscess (can also lead to pulmonary abscess and a clotted IJ vein) “Lemierres Syndrome”Retropharyngeal Abscess(remember the rule 7mm at C2 and 22mm and C7)What diseases mimic streptococcal infection and how?ConditionSigns and Symptoms(“Mononucleosis”)- caused by RBV or CMVLooks a lot like strep (have exudates just like strep)May have exudate or may notMay have rash (classically after antibiotics given)Enlarged spleen/Abd Pain—Make sure patient refrains from contact activities for 6 weeksMay have leukopeniaAcute HIVUsually do not have exudate on tonsilsOften have painful ulcers in the mouth (look like canker sores)Fever, headaches, malaise, arthralgiasPertussis1/3 of patients have a gray membrane on posterior pharynx, persistent coughGonorrhea or ChlamydiaUsually asymptomaticMake sure you take a sexual history (including oral sex for women)May have associated arthralgias or even septic arthritisFrequency of various conditions:Rational ExamWhat to pay attention to in history and physicalHistory:Physical:Sexual historyFeverExposures to others with illnessExudate on TonsilsPresence of CoughCervical LADGeneral health (weight loss)SmokerTesting and Testing:Understanding testing threshold, pretest probability, sensitivity and specificity, Liklihood Ratios and treatment threshold are key to understanding how/why we perform rapid strep testing as well as perform culture.Testing Threshold—what percentage of patients are you willing to send out your door who may be positive, without further testing?We set this number based on the severity of missing a diagnosis; for example, if a condition is quite serious (heart attack or PE, we might set this number at 1%), for strep throat, we might set this number higher, at 5%Pretest Probability: This is how likely it is that you think a patient may have an illness. This number is affected by disease prevalence. How does this number change in different demographics or in different clinical settings?Demographics: In college students, the pretest probability of EBV may be 25 or 30%, but for a 65 year old, it might be 5%. Practice Settings: It may also be affected by where a patient presents—In patients with chest pain, the pretest probability of a MI in the ED may be 10%, while in the OP clinic, it may be 2%Clinical decision rules can be used to set pretest probability, the ones used for strep testing include the centor criteriaCentor Criteria for two patientsTo understand how this decision rule also proposed a therapy, we need to consider the Likelihood Ratios of a given test, our treatment threshold and Post test ProbabilityTreatment Threshold: how certain you have to be that a patient has a condition in order to decide to treat. What affects treatment threshold?Costs of therapy (both in terms of risks to patients as well as financial costs)The potential benefit of therapy The risks of not treating. What are these for strep throat?Glomerulonephritis, myocarditis, retropharyngeal abscess, PANDAS, rheumatic disease, etc. (HIGH RISKS)For example, guidelines for recommending statin therapies, suggest that the 10 year risk of MI exceed 7.5% over 10 years prior to recommending statins.For strep throat, since antibiotics are cheap and relatively safe, we might set this number at 50%. The number is low because the risks of antibiotics are low and the risk of missing and not treating GAHBS are high.Now lets consider Test Characteristics:Sensitivity-(True Positive)-Test will be positive if you have disease, but may have high rate of false positives. (used for screening tests) Specificity: (True Negative)- use for confirmatory testing. Test will be negative if you do not have the diseasePPV: If the patient has a positive test, how likely the patient has disease (depends on disease prevalenceNPV: if the patient has a negative test, how likely the patient does not have disease (depends on disease prevalence)+LR: how much the prosttest probability changes with a positive test (test characteristic)-LR: how much the posttest probablity changes with a negative test (test characteristic)For Rapid Strep TesetingSensitivity Specificity (True Negative)- use for confirmatory testing. Test will be negative if you do not have but may give you false negatives+ LR: (characteristic of test)-LR ratio: (characteristic of test)Rapid Strep Testing65%97%180.21PPV (depend on prevalence of disease)NPV (depend on prevalence of disease)81%93%How to Apply EBM (Rational Clinical Exam, EBM Guide)I set my testing threshold at 5%Set my treatment threshold at 50%--the risk of antibiotics are low risk, devastating if patient developed Rheumatic Heart ConditionI calculate my pretest probability for my two patients above For one patient (see above) the Centor Criteria tell me to treat empirically (I have exceeded my treatment threshold)For the second patient, in whom my pretest probability was 30%. I use a Fagan Nomogram to help me convert pretest probability to post test probability using Liklihood Ratios.A positive RADT gives me post test probability of 85%, higher than my testing threshold, so I will treatHowever, a negative RADT gives me a post test probability of 7.5% and that is still above my testing threshold, so I need the culture to test furtherTreatment for Strep Throat (from CDC and 2013 IDSA guidelines)Amoxicillin 500mg-875mg BID for adults (depending on severity) x 10 daysPenicillin injection: 1.2 * 106 unites injected one timeKeflex is another alternative 500mg BID x 10 daysSecond tier therapy for PCN allergic patientsClindamycin 300mg TID 2 10 daysAzithromycin 500mg once daily for 5 daysTips for Patients Receiving Abx (from CDC)Antibiotics increase the risk of resistanceMUST TAKE ENTIRE DOSE, even though you feel better after 3-4 days; you are still infectious for others, and you can “re-catch” the strep or have it recur if you don’t complete all your medicationsRecommend patient specific symptomatic therapy –sprays with topical anesthetics, ibuprofen and acetaminophenTest for Cure/RelapsesConsider Culture with testing for resistance if household contacts spread illness among themselves!In households with proven GAHBS, you should perform a TEST OF CUREIn patients with symptoms that do not resolve, consider household reservoirs, or alterative diagnoses (HIV, EBV, Gonorrhea, Abscess formation, etc)References:AAFPJAMA Rational Clinical ExamCDC and IDSA treatment guidelines for GAHBSUp to Date ................
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