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A Sputum Screening Test to Rule Out Pneumonia at an Early Stage With High Negative Predictive Value

Ramezani, Amir, MD*†; Eng, Lars, PhD; Turkina, Maria V., PhD§; Theodorsson, Annette, PhD, MD*†; Nayeri, Fariba, PhD, MD

doi: 10.1097/POC.0000000000000170
Original Article

Background Pneumonia is a serious and widespread cause of morbidity and mortality. At an early stage, the symptoms are similar to other respiratory disorders, and there is no single criterion standard for diagnosis. Antibiotics are used too often as a precaution.

Objectives The objective of this study was to perform an assessment and clinical evaluation of a rapid sputum screening test (index test) to rule out pneumonia.

Methods Leftover sputum samples (467) collected at the Department of Microbiology from November 2016 to March 2017 were blindly analyzed within 72 hours with the index test. The clinical accuracy of the test was estimated for pneumonia by comparison with the established diagnosis by independent physicians (International Classification of Diseases, 10th Revision). Hepatocyte growth factor and calprotectin were measured on random samples (80), and layman volunteers (40) were asked to perform the test on artificial samples.

Results Two of 73 cases of pneumonia (community-acquired and nosocomial) showed negative results by the sputum strip test (97% sensitivity and 94% negative predictive value). The test results were highly correlated to hepatocyte growth factor and calprotectin concentrations in samples (R2 = 67% respective 39%). Importantly, all of the volunteers were able to estimate the correct positive and negative results.

Conclusions The novel rapid sputum test represents a feasible tool for screening and ruling out the overwhelming majority of nonsevere respiratory infections at primary care settings, at home or when properly equipped laboratories are not available.

From the *Division of Neuro and Inflammation Science, Department of Clinical and Experimental Medicine, Linköping University;

Department of Neurosurgery, Anesthetics Operations and Specialty Surgery Center Region Östergötland;

The Institute for Protein Environmental Affinity Surveys (PEAS Institute); and

§Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.

Reprints: Fariba Nayeri, PhD, MD, The Institute for Protein Environmental Affinity Surveys (PEAS Institute), Linköping, Sweden. E-mail:;

Authors’ contributions: AR participated in design of study and carried out the studies on paper journals, gone through the medical history in data journals, joined preclinical studies on samples and analysis of data and drafted the manuscript. LE participated in design of study and carried out SPR and ELISA, performed the statistical analysis and drafted the manuscript. MVT carried out preclinical studies on samples and analysis of data and drafted the manuscript. AT participated in the conception and design of the study, interpretation of results and drafted the manuscript. FN carried out studies on paper journals, participated in study design, interpretation of results and coordination and drafted the manuscript.

FN has grounded PEAS Institute, holding approved patents (P8808) related to sulfated glycan-binding proteins in detection of infection. The other authors declare no conflict of interest.

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