Chest
Volume 121, Issue 5, May 2002, Pages 1486-1492
Journal home page for Chest

Clinical Investigations
Pneumonia
Applying Sputum as a Diagnostic Tool in Pneumonia: Limited Yield, Minimal Impact on Treatment Decisions

https://doi.org/10.1378/chest.121.5.1486Get rights and content

Study objectives

We evaluated the role of sputum examination in the management of patients with community-acquired pneumonia (CAP) in a primary-care hospital without microbiologic laboratory facilities.

Design and interventions

A diagnostic strategy using regular collection of sputum samples, Gram staining in a local laboratory, and mailing of samples to a commercial laboratory for culture analysis.

Setting

A 200-bed primary-care hospital without subspeciality physicians.

Patients

One hundred sixteen consecutive patients with a diagnosis of CAP were prospectively evaluated during a 12-month period.

Results

Of 116 patients, 42 patients (36%) were capable of producing a sputum sample. Age ≥ 75 years (odds ratio [OR], 0.4; 95% confidence interval [CI], 0.18 to 0.93) and prior ambulatory antimicrobial treatment (OR, 3.2; 95% CI, 1.2 to 8.4) were independent predictors of sputum production. A delay in collection and processing of sputum samples of > 24 h was present in 31% and 39%, respectively. A delay in collection yielded an increased number of Gram-negative enteric bacilli and nonfermenters (44% vs 7%, p = 0.056). A delay in processing was associated with an increased number of Candida spp isolates (33% vs 9%, p = 0.16). The overall diagnostic yield was low (10 of 116 patients, 9%) due to a limited number of valid samples (n = 23 of 42 patients, 55%) and a limited number of definitely or probably positive samples on Gram's stain and culture (n = 10 of 42 patients, 24%). Prior ambulatory antimicrobial treatment was associated with a reduction in diagnostic yield (14% vs 56%, p = 0.09). The impact of diagnostic results on antimicrobial treatment decisions was minimal, with antimicrobial treatment directed to diagnostic results in only one patient.

Conclusions

We conclude that in this setting representative of primary-care hospitals in Germany, sputum had a low diagnostic yield and did not contribute significantly to patient management.

Section snippets

Study Hypothesis

The study was part of a follow-up interventional evaluation of the management of patients with CAP at the Dreifaltigkeits-Krankenhaus in Wesseling, a primary-care hospital with about 200 beds.16 One part of the intervention consisted of evaluation of sputum samples as a diagnostic tool. The study hypothesis was that the sampling of sputum in this setting would result in a low diagnostic yield with a minimal impact on antimicrobial treatment decisions. The other part of the study included the

General Patient Characteristics and Outcome

The patient population included 72 men and 44 women (62% and 34%, respectively). Mean age was 68 ± 16 years (range, 24 to 96 years), including 82 elderly patients (71%; age ≥ 65 years) of whom 50 patients (43%) were very elderly (age ≥ 75 years). Twenty-four patients (21%) were admitted to the hospital from nursing homes. At least one comorbidity (cardiac, pulmonary, hepatic, renal, CNS, diabetes mellitus, or neoplastic as previously defined18) was present in 103 patients (89%). Using the

Discussion

The present study demonstrates the limited value of sputum as a diagnostic tool in the initial evaluation of patients with CAP admitted to a primary-care hospital. The limitations include failure to obtain a sputum sample from most patients, delay in collection and laboratory processing of samples, low diagnostic yield, and minimal impact on therapeutic decisions.

Of the 42 sputum samples collected from this population of 116 patients, only 23 samples (55%) were valid when standard microscopic

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