The Laboratory Diagnosis of Pneumonia: The Role of the Community Hospital Pathologist

Utility of gram staining for evaluation of the quality of cystic fibrosis sputum samples

The microscopic examination of Gram-stained sputum specimens is very helpful in the evaluation of patients with community-acquired pneumonia and has also been recommended for use in cystic fibrosis (CF) patients. This study was undertaken to evaluate that recommendation. One hundred one sputum samples from CF patients were cultured for gram-negative bacilli and examined by Gram staining for both sputum adequacy (using the quality [Q] score) and bacterial morphology. Subjective evaluation of adequacy was also performed and categorized. Based on Q score evaluation, 41% of the samples would have been rejected despite a subjective appearance of purulence. Only three of these rejected samples were culture negative for gram-negative CF pathogens. Correlation between culture results and quantitative Gram stain examination was also poor. These data suggest that subjective evaluation combined with comprehensive bacteriology is superior to Gram staining in identifying pathogens in CF sputum.

Intra and inter technologist variability in the quality assessment of respiratory tract specimens

The majority of microbiology laboratories have implemented quality improvement procedures such as a Q scoring system to assess the nature of clinical specimens. Our study reviewed the sources and the amount of variation when Q scoring of lower respiratory secretions was performed. In total, 450 slides representing lower respiratory tract secretions were Q scored by three experienced technologists. Total agreement regarding the number of neutrophils, squamous epithelial cells and Q scores was 76%, 57% and 57% respectively. The major factor influencing Q score values was the enumeration of epithelial cells. From our findings, we expect that there is greater variability in Q scoring then is generally acknowledged and there is a substantial degree of subjectivity on part of individual technologists reading gram stains.

Commentary on the 1993 American Thoracic Society guidelines for the treatment of community-acquired pneumonia

Early treatment of community-acquired pneumonia (CAP) is associated with improved outcome. Since extensive diagnostic testing identifies an etiologic agent in only half of the cases and usually requires several hours or even days for results, CAP is most often initially treated empirically. In 1993, the American Thoracic Society (ATS) established guidelines to assist primary care physicians in antibiotic selection for the initial empiric treatment of CAP in immunocompetent adults. Since publication of the guidelines, the incidence of certain bacteria has been redefined, antimicrobial resistance patterns have changed, risk factors for stratifying need for hospitalization have been further defined, and newer antibiotics have been introduced. These changes necessitate a reevaluation of the 1993 ATS guidelines. This article proposes a modification of the ATS guidelines. This modification continues to classify patients into groups, based on specific risk factors, to which a limited number of likely pathogens are identified and for which antibiotic treatment regimens are developed. The modification differs from the original ATS guidelines because of the changes in risk factors. Patient groups are still broadly divided into outpatient and inpatient care, but earlier risk factors of age and coexisting illness have been refined. Risk factors suggested herein as considerations to guide treatment include the presence of cardiopulmonary disease, history of smoking, severity of illness, risk of drug-resistant Streptococcus pneumoniae and Pseudomonas aeruginosa, and need for ICU admission.