The value of outpatient blood cultures in the emergency department

Original Contributions

The Value of Outpatient Blood Cultures in the Emergency Department DAVID P. SKLAR, MD,* ROBERT RUSNAK, MDt Thevalue of edull outpetlentblood cultureswas aeeeeeedby a retroepectlve chart reviewof all ptlente for whom cultureewe obtainedIn an emergency depaflment.Elghty*lx of 411 pstlentefor whom cultureswere obtainedwere not edmltted.Five of these 66 pntlentswere ldentMedae beingbectemmk by poeltlveblood culture growth the next dey, and three of the five hed enda cardltlr. All endocardltleptlente had ldentlfiabk rkk factorsfor thle dleeaee. Althoughbloodculturescannotbe recommended for mostpetlentsdlecharged from the emergencydepartmentwith a febrile lllnees, they are helpful In da tectlng endocerdltlsand other bacteremlccondltlonebefore obvlous signs develop.(Am J EmergW 1987; 595-l 00)

Emergency department blood cultures are expensive, provide no immediate information, and produce about as many false-positive (contaminant) as true-positive results, thus causing needless work and worry for both the patient and the physician. lv2 Although the use of outpatient blood cultures has greatly enhanced the diagnosis and treatment of children with occult bacteremia,3*4 its value in adult outpatients has not been demonstrated. Previous studies have concluded that use of blood cultures in adult patients discharged from the emergency department resulted in a high cost for a minimal return.‘*’ However, in one of these studies, cultures were obtained for all febrile adult patients,’ and in the other, most positive cultures were contaminants.2 In clinical practice, cultures are not obtained for all febrile adults; instead, physicians must depend on clinical judgment to decide when to obtain cultures and which patients to admit to the hospital and which patients to discharge. Because blood cultures require at least 24 hours to demonstrate growth, the emergency physician sometimes is conFrom the ‘Division of Emergency Medicine, Department of Family, Community and Emergency Medicine, University of New Mexico School of Medicine, Albuquerque, New Mexico; and the Department of Emergency Medicine, Hennepin County Hospital, Minneapolis, Minnesota. Manuscript received May 8, 1988; accepted June 6, 1986. Address reprint requests to Dr. Sklar: Division of Emergency Medicine, University of New Mexico School of Medicine, 620 Camino de Salud, N.E., Albuquerque, NM 87131. Key Words: Bacteremia, endocarditis. outpatient blood cultures, septicemia.

fronted with the difficult clinical situation of the patient with apparently low-risk factors for bacteremia who does not appear to warrant admission to the hospital at that time. In such instances, the physician may draw the blood cultures and admit the patient, or forgo the blood cultures and discharge the patient (potentially delaying the diagnosis of bacteremia), or draw the blood cultures and discharge the patient. Our study explored the use of blood cultures in patients discharged from the emergency department at the time that blood cultures were obtained, because the prevalance and efficacy of this clinical practice are unknown. MATERIALSAND METHODS The University of New Mexico Hospital Emergency Department has approximately 40,000 patient-visits a year. Eleven percent of these patients are admitted to the hospital. From January 1983 through October 1984,411 adult patients seen at the University of New Mexico Hospital Emergency Department had blood cultures drawn and had charts

AMERICAN JOURNAL OF EMERGENCY MEDICINE W Volume 5, Number 2 n March 1987

Contaminants were distinguished from the positive cultures based on the clinical course, type of organism, and number of positive cultures according to established criteria.6,7Oral temperature was measured unless the patient was unable to hold an oral thermometer effectively or was breathing more than 20 times a minute, in which case the rectal temperature was measured.8 Statistical comparison of the bacteremia rates for the discharged and admitted patient groups was performed by chi-square analysk9 RESULTS Four hundred and eleven charts were reviewed. Seventynine percent (3251411) of those patients from whom blood cultures were obtained were admitted immediately to the hospital, and 7.4% (24/325) of these were proven bacter-

emit (Table 1). These bacteremic inpatients had an average age of 55.4 years and average temperature of 39.3”C. Twenty-one percent (86/411) of patients from whom blood cultures were drawn were discharged from the emergency department. Of these outpatients, five (5.8%) developed true-positive blood cultures based on repeat positive cultures, clinical course, and/or presence of a pathogenic organism.6.7 This represented 17% (5129) of the total cases of proven adult bacteremia seen in our emergency department during the study period. There was no statistically significant difference between the rate of bacteremia in the admitted and discharged groups. (x2 = 0.255; DF = 1; P > 0.6) The individual case reports of patients who were discharged with subsequent bacterial growth in their blood cultures follow.

TABLE1. Patients Initially Admitted with Positive Cultures Age (Years)

Temperature (“C)

77

39.6

Urosepsis

70 71 75

39.6

17 63 86

38.8 37.2 39.5

46 60 73 24

38.8 35.9 39.0 40.5

22

39.2

Urosepsis Urosepsis Pneumonia, meningitis Pyelonephritis Pneumonia Multiple-abcesses of kidney Pyelonephritis Septic arthritis Urosepsis Septic shock, asplenia Septic abortion

62

40.0

72 46

40.6 40.4

41 87

39.5 39.0

31

39.2

89 29

40.0 40.5 39.1

24

38.5 39.9

39.8

54 46

96

38.8

Diagnosis

Septic shock, pancytopenia Pyelonephritis Cellulitis Pyelonephritis Sepsis, hyperosmolar coma Urosepsis, pyelonephritis Urosepsis Ruptured appendiix Postpartum endometritis Psoas abscess Osteomyelitis Pneumococcal

Organism

Days of Stay

Klebsiella pneumoniae and Escherichia coli Klebsiella pneumoniae Proteus mirabalis Streptococcus pneumoniae

1 (Death) 3 6 (Death) 0 (Death)

Escherichia coli Staphylococcus aureus Klebsiella pneumoniae

6 9 8

Escherichia coli Staphylococcus aureus Escherichia coli Streptococcus pneumoniae Streptococcus group A p hemolytic Enterobacter aerogenes Escherichia coli Streptococcus group A beta-hemolytic Escherichia coli Streptococcus fecalis

6 3 (Death) 13 1 (Death) 9

13 (Death) 9 11 5 6

Escherichia coli

7

Escherichia coli Bacteroides sp Clostridium perfringes

5 5 7

aureus Staphylococcus Streptococcus

54

26 7

SKIAR AND RUSNAK n BLOOD CULTURES IN THE EMERGENCY DEPARTMENT

Case1 A 22-year-old woman presented to the emergency department with a chief complaint of 2 weeks of bifrontal headaches and fever. She had a history of rheumatic fever as a child but no medical problems as an adult. Her physical examination was notable for a temperature of 37.9”C, blood pressure of 100/72 mm Hg, pulse of 112 bpm, and a grade II-III/VI holosystolic murmur in the left axillary region. The rest of the physical examination was unremarkable. She had a normal spinal tap and was discharged after blood cultures were drawn. The next day, the blood cultures grew grampositive cocci in chains later identified as a-hemolytic streptococci. The patient was called back to the hospital and admitted, where she remained for one month’s treatment of bacterial endocarditis. Endocardiography and repeated cultures positive for a-hemolytic streptococci confirmed the diagnosis of bacterial endocarditis. Case 2 An l&year-old intravenous drug abuser came to the emergency department with vague joint aches, fever, headache, and photophobia. On physical examination, he had an oral temperature of 37.2”C, blood pressure of 1lo/56 mm Hg, and a pulse of 76 bpm. His physical examination was entirely normal, including the absence of heart murmurs and joint effusions. Several nonspecific healing skin lesions that appeared to be from excoriations or drug injections were evident. His chest radiograph was normal, but his urinalysis showed 40 to 50 leukocytes per high-power field, and he was thought to have an infection of the genitourinary tract. Blood cultures were drawn, and the patient was discharged with a prescription for ampicillin. The next day, he returned to the emergency department with worsening joint pain and was admitted; at this time, the blood cultures drawn in the emergency department were growing gram-positive cocci later identified as Scuphylococcus aureus. The patient subsequently developed purulent S. aureus arthritis in multiple joints, changing heart murmurs, and multiple blood cultures positive for S. aureus. After one month of antibiotic treatment, he recovered and left the hospital. Case 3 A 47-year-old diabetic woman on renal dialysis presented to the emergency department with fever, nausea, diarrhea, vomiting, and general malaise. The patient had missed her dialysis the day before because she felt too ill to travel. On physical examination, she had a temperature of 38.4”C, a pulse of 104 bpm, and blood pressure of 140/70 mm Hg. She had a grade II/VI early systolic ejection murmur, but otherwise her examination was unremarkable. A chest radiograph revealed cardiomegaly, which had increased from

that noted on a radiograph done one year earlier. She was discharged from the emergency department with a diagnosis of gastroenteritis, but blood cultures were drawn, and the patient was sent to the dialysis center the next morning. At the dialysis center the patient again reported her fever and malaise, and blood cultures again were drawn. That evening, the cultures drawn in the emergency department were noted to be growing gram-positive cocci and the patient was contacted by telephone. She returned to the hospital where she was treated for S. aureus endocarditis. Further blood cultures confirmed the diagnosis of S. aureus endocarditis as did echocardiograms showing vegetations on the aortic valve. The patient recovered uneventfully after treatment with vancomycin was completed. Case 4 A 17-year-old girl came to the emergency department with nausea, vomiting, flank pain, and fever. She had no other medical problems and was not noted to have any vomiting in the emergency department although she drank water. A physical examination revealed an oral temperature of 39.3”C, a pulse of 100 bpm, and blood pressure of 115172 mm Hg. The cardiac examination was unremarkable; specifically, no murmurs were noted. She had right flank pain to percussion. Her leukocyte count was 14.4 thousand with 81 neutrophils, 10 band forms, four lymphocytes, and five mononuclear cells. Urinalysis revealed 15 to 20 leukocytes per high-power field and many bacteria without any casts. The patient was started on ampicillin, 500 mgm by mouth every six hours, and blood cultures were drawn. Blood cultures grew gram-negative rods later identified as Es&erichia coli, which had the same sensitivities as E. coli growing in her urine. The patient returned to the hospital for admission after being called at home. Her physical examination on admission was unchanged from the initial examination. She remained in the hospital for two days of intravenous antibiotics followed by oral antibiotics and recovered without complications. Case 5 A 27-year-old man presented to the emergency department complaining of back and chest pain with fever that had lasted for a week. He had a history of smoking and occasionally noted a morning cough. He had a history also of rheumatic fever as a child. On physical examination his chest was clear to percussion and auscultation; a grade IV/VI systolic murmur was present. The chest radiograph revealed no abnormality. He was thought to have a viral syndrome or possibly an exacerbation of bronchitis. After blood cultures were drawn, he was discharged with a prescription for ampicillin, 500 mgm by mouth every six hours. The blood cultures grew gram-positive cocci later identified as Srrep-

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The patient was contacted for admission but refused to return to the hospital for unknown reasons. He was lost to follow-up procedures for six months before he was recontacted. He reported feeling well and refused evaluation. tococcus pneumoniae.

DISCUSSION Inapparent septicemia is in some ways similar to acute myocardial infarction. Symptoms and signs may be nonspecific, and accurate confirmation of the diagnosis may require 24 to 48 hours. Delay in diagnosis may result in increased morbidity or even death. However, admission of patients without the disease is very costly and may actually increase morbidity for those erroneously admitted. lo. Specific clinical correlates to positive laboratory, electrocardiographic, and radiologic findings have been published to assist clinicians in determining the probability of myocardial infarction.” High-risk patients may then be admitted, whereas low-risk patients may be safely discharged. A similar predictive instrument for improving the diagnostic accuracy of inapparent bacteremia in adults does not exist. A previous study of febrile adults defined high and low risks for bacteremia based on nonspecific clinical criteria used for admission.’ A recommendation against the routine use of blood cultures to diagnose bacteremia in febrile adults not admitted to the hospital was made. However, in clinical practice cultures are not obtained from all febrile adults, and, occasionally, cultures are obtained from afebrile patients. Various mitigating factors such as underlying condition, level of fever, age, and current diagnosis may influence the physician’s decision concerning the need for blood cultures. These same factors may not appear sufficient to require admission to the hospital, and the patient may then be discharged. In our study 86 patients were discharged after blood cultures were drawn. Three-hundred-and-twenty-five patients had their blood cultured and were admitted. Five (5.8%) of the discharged patients (Table 2) were identified as having positive cultures compared to 24 (7.4%) of the admitted patients (Table 1). The actual difference in the rate of bacteremia between these two groups was neither statistically nor clinically significant. These results shed doubt on the

accuracy of physicians’ clinical judgment in distinguishing bacteremic from nonbacteremic adults. There may be many reasons for this lack of accuracy including the noisy, hectic emergency department environment; the unpredictable nature of the entities involved; or the limited time available in the emergency department to elicit an accurate history. Regardless of the responsible factor, the use of blood cultures on patients discharged from the emergency department hastened the diagnosis and/or treatment of five patients who otherwise might have suffered progression of their illness or even death before a definitive diagnosis could be established. We particularly wish to emphasize the usefulness of this test in the diagnosis of early endocarditis. All of the patients with endocarditis seen in the emergency department during the 22-month study period were initially discharged but had cultures taken at the time of the initial visit and admitted the following day. The insidious nature of endocarditis is well known. ‘* Staphylococcal endocarditis may present without a heart murmur and may be diagnosed only at autopsy in half of the cases.13 Review of the charts of the affected patients revealed that obvious signs such as embolic phenomena, changing murmurs, and petechiae were absent. The temperature was normal in one case, barely elevated in a second, and only moderately elevated in a third. Identifiable risk factors for endocarditis (Table 3) were present in all three confirmed cases and included intravenous drug use, I4 rheumatic heart disease,i5,16 and hemodialysis. I7 We were able to identify 11 other patients with risk factors for endocarditis who presented to the emergency department with a febrile illness.‘4-24 Based on the clinical impression of the attending physician, two of these patients were admitted for two days and discharged after cultures remained negative for growth and echocardiographic findings were unremarkable. The other nine patients were discharged after clinical evaluation, had no growth from blood cultures, and did not develop evidence for endocarditis. Without a definitive diagnosis, we do not believe that any of the discharged patients with risk factors for endocarditis would have been treated with antibiotics during the time that the cultures were growing. No obvious morbidity occurred to the three patients with confirmed endocarditis between culturing and admission to the hospital.

TABLE2. Patients Initially Discharged with Positive Cultures Age (Years)

Temperature [“C)

Diagnosis

Underlying Illness

22

37.9 37.2 38.4 39.3 38.4

Endocarditis Endocarditis Endocarditis Pyelonephritis Unknown

Rheumatic heart disease Intravenous drug abuse Renal failure on hemodialysis None Rheumatic heart disease

18

47 17 27*

‘All patients were admitted the next day except patient five who was contacted and refused further treatment.

98

Organism a-hemolytic streptococcus Staphylococcus aureus Staphylococcus aureus Escherichia co/i Streptococcus pneumoniae

SKlAR AND RUSNAK n BLOOD CULTURES IN THE EMERGENCY DEPARTMENT

,

Beyond the prevention of valvular destruction and death, the usefulness of outpatient blood cultures in the early diagnosis of endocarditis becomes more controversial. We were able to identify one patient with pyelonephritis with bacteremia originally treated as an outpatient. Response of this condition to oral antibiotics and outpatient treatment is not known, but because shock has been associated with gram-negative bacteremia in up to one third of cases,25 admission of all such patients to the hospital for intravenous treatment would appear warranted. Recently, the outpatient management of pyelonephritis has been advocated.26 Because bacteremia may be associated with pyelonephritis in 16 to 61% of cases,27.28blood cultures may be useful in the management of patients with pyelonephritis who are discharged. The same argument can be made for patients with pneumococcal pneumonia, an entity associated with bacteremia in 10% of casesz9 and presently considered amenable to outpatient treatment. 3o Pneumococcal pneumonia with bacteremia occurred in 50% of the cases of positive blood cultures discovered by Eisenberg et al.’ in their study of emergency department bacteremia, and it presents a definite risk in outpatients as hospitalization criteria change. Although none of our discharged patients had bacteremic pneumococcal pneumonia, one of our patients did have pneumococcal bacteremia of uncertain cause (see subsequent discussion). Discharge of a patient after blood cultures have been obtained mandates follow-up evaluation of both the culture results and the patient. Special precautions must be taken, including verification of telephone numbers or designation of a relative for contact. In the absence of certain followup evaluation due to social, psychological, or financial impediments, hospitalization of the patient is preferred over outpatient management. The patient with pneumococcal bacteremia eluded followup evaluation. Although contacted later, he refused hospitalization or any further care. We believe the most likely diagnosis for this patient was pneumococcal endocarditis, pneumococcal pneumonia not apparent on radiography or pneumococcal bacteremia without any identifiable focus.31 This scenario represents the major risk of outpatient blood cultures: loss of the patient. Emphasis on the importance of proper treatment prior to discharge and good communications between physician and patient should minimize such occurrences. Another problem of outpatient blood cultures is the occurrence of false-positive or contaminant results that initially may not be identifiable as such. In our study, there were 20 contaminants (4.9%), which is similar to the 4.8% noted previously. I Others have reported higher contaminant rates in the emergency department,2 making follow-up evaluation confusing and costly. Careful use of aseptic technique can

TABLE3. Risk Factors for Infective Endocarditis Congenital heart disease’5.‘6 Ventricular septal defect Tetralogy of Fallot Pulmonic stenosis, aortic stenosis Complex cyanotic heart disease Patient ductus arteriosis Systemic to pulmonary shunts Valvular heart disease’5.16 Rheumatic heart disease Acquired valvular heart disease Calcific aortic stenosis Mitral valve pro1apse17~‘g Valvular damage from previous endocarditis Prosthetic valves15,20 Narcotic addiction14 Electronic pacemakers21-23 Idiopathic hypertrophic subaortic stenosisz4 Hemodialysis”

produce acceptable levels of contaminated cultures; however, even with low contaminant rates, the false positives approach the true positives and must be considered a potential side-effect of the procedure. Use of multiple sets of blood cultures on the same patient allows for easier identification of contaminants while increasing the sensitivity of detecting bacteremia, but it also increases the cost of the procedure. 5 There may be enormous economic benefits associated with the selective use of outpatient blood cultures. We estimate that with the use of outpatient blood cultures the cost of discovering each case of inapparent bacteremia was $877 ($51 per set of blood cultures times 86 patients tested and discharged divided by five positive cases identified). Admission of all patients from whom blood was cultured would have cost $12,910 for each case of occult bacteremia discovered-86 patients admitted times $800 room charges for two days divided by five positive cases identified. Total savings for discovering five cases of bacteremia with outpatient blood cultures would be $60,165. Discharge without taking cultures from the 86 patients not admitted could have delayed the diagnosis of the positive patients, potentially resulting in increased morbidity to them and increased the cost in caring for them. Until the risks for development of bacteremia can be more carefully defined based on clinical signs or until an immediate test to confirm bacteremia becomes available, the use of blood cultures on selected adult outpatients offers the advantages of improving and hastening diagnostic accuracy without the cost of needless admission. Patients who may benefit most from this test are those at risk for endocarditis who have a history of febrile illness and no signs of endocarditis, those with pyelonephritis, and possibly those with pneumococcal pneumonia, when follow-up evaluations for such patients can be assured.

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AMERICAN JOURNAL OF EMERGENCY MEDICINE n Volume 5, Number 2 n March 1987

SUMMARY Blood

pneumococcal Although blood cultures are not indicated routinely in febrile adults with nonfocal illness who are those with risk factors for endocarditis, those with pneumonia, and those with pyelonephritis

1. Eisenberg JM, Rose JD, Weinstein A. Routine blood cultures

from febrile outpatients. JAMA 1978;236:2863-2865 2. Stair TO, Lenhan M. Outpatient blood cultures; Retrospective and prospective. Audits in one emergency department (letter). Ann Emerg Med 1984;13:986-987 3. McGowen JE, Bratton L, Klein JO, et al. Bacteremia in febrile children seen in a walk-in pediatric clinic. N Engl J Med 1973;288:1309-1312 4. McCarthy P, Dolen T. Hyperpyrexia in children. Am J Dis Child 1976;13:849-851 5. Lewis JF, Alexander JJ. Blood cultures in bacteremia. South Med J 1982;75:147-150 6. Kotin P. Techniques and interpretation of routine blood cultures. JAMA 1952; 149:1273-l 276 7. MacGregor R, Beaty HH. Evaluation of positive blood cultures. Arch Intern Med 1972;130:84-87 6. Tandberg D, Sklar D. Effect of tachypnea on the estimation of body temperature by an oral thermometer. N Engl J Med 1983;308:945-946 9. Loftis G, Loftis E. Essence of Statistics. Monterey, California, Brooks/Cole, 1982:508-530 10. Steel K, Gertman PM, Grescenzi C, et al. latrogenic illness on a general medical service at a university hospital. N Engl J Med 1981304638-642 11. Goldman L, Weinberg M, Weisberg M, et al. A computer derived protocol to aid in the diagnosis of emergency room patient with chest pain. N Engl J Med 1982;307:588-596 12. Lerner PT, Weinstein L. Infective endocarditis in the antibiotic era (continued). N Engl J Med 1966;274:259-266

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13. Lerner PT, Weinstein L. infective endocarditis in the antibiotic era. N Engl J Med 1966;274:199-201 14. Luttgens WF. Endocarditis in main line opium addicts. Arch fntern Med 1949;83:653-664 15. Kaplan EL, Bascom AR, Bisno A, et al. Prevention of bacterial endocarditis. Circulation 1977;56:139a-143a 16. Everett ED, Hirschmann JV. Transient bacteremia and endocarditis prophylaxis. A review. Medicine 1977;56:61-77 17. Goldblum SE. Endocarditis in a hemodialysis unit. N Engl J Med 1983;308:525 18. Clemens JD, Horwitz RI, Jaffee CC, et al. A controlled evaluation of the risk of bacterial endocarditis in persons with mitral-valve prolapse. N Engl J Med 1982;207:776-781 19. Lachman AS, Bramwell-Jones DM, Lakier JB, et al. Infective endocarditis in the billowing mitral leaflet syndrome. Br J Heart 1975;37:326-330 20. Block PC, De Sanctis RW, Weinberg A, et al. Prosthetic valve endocarditis. J Thorac Cardiovasc Surg 1970;60:540-548 21. Case Records of the Massachusetts General Hospital. (Case 36-1980) N Engl J Med 1980;303:628-636 22. Bryan CS, Sutton JP, Saunders DE Jr, et al. Endocarditis related to transvenous pacemakers, syndromes and surgical implications. J Thorac Cardiovasc Surg 1978;75:758-762 23. Schwartz IS, Pervez N. Bacterial endocarditis associated with a permanent transvenous cardiac pacemaker. JAMA 1971;218:736-737 24. Kaye D. Prophylaxis for infective endocarditis: An update. Ann Intern Med 1986;104:419-423 25. Gleckman R, Blagg N, Hibbert D. Community-acquired bacteremit urosepsis in the elderly patients. A prospective study of 34 consecutive episodes. J Urol 1982;128:79-81 26. Abraham E, Baraff L. Oral versus parenteral therapy of pyelonephritis. Curr Ther Res 1982;31:4536-4542 27. McMurdock J, Speirs CF, Gedds AM, et al. Treatment of recurrent urinary tract infection. In O’Grady FO, Brumfitt W (eds). Urinary Tract Infection. London, Oxford University Press, 1968:227-234 26. Gleckman R, Blagg N, Hilbert D, et al. Acute pyelonephritis in the elderly. South Med J 1982;75:551-554 29. Dorff GJ, Rysel MW, Farrer SG, et al. Etiologies and characteristic features of pneumonias in a municipal hospital. Am J Med Sci 1973;266:349-358 30. Seigel D. Management of community acquired pneumonia. West J Med 1985;142:45-48 31. Spitalny KC, Bromberg K, Ginsberg M. Streptococcus pneumonia bacteremia without an identifiable focus in adults. Johns Hopkins Med J 1982;150:35-37