A Systematic Review and Meta-Analysis of Sputum Purulence to Predict Bacterial Infection in COPD Exacerbations

Figures & data

Figure 1. Flow chart diagram of screening studies.

Table 1. Characteristics and outcome values of included studies.

Reference	Study design, country	Participants and Setting	Anthonisen criteria	Sputum collection	Sputum description	Sample size	PPM positive rate
							Purulent	Mucoid
Allegra 2005 [10]	Prospective cohort study, Italy	COPD exacerbation	Not reported, (Moderate or severe exacerbation)	Expectoration	Sputum was analyzed by a qualiquantitative colorimetric scale. Samples with white or gray preponderance were considered as mucoid, whereas shades of yellow, green, and brown were considered as purulent.	581	414/436 (95.0%)	113/145 (77.9%)
		Hospital (477/795 patients)
		Non-hospital (318/795)
Daniels 2010 [11]	Prospective cohort study, Netherland	COPD exacerbation Hospital	Type I or II	Expectoration	Sputum color was assessed with a previously validated five-point sputum color chart (BronkoTest; Heredilab Inc., Salt Lake City, UT, USA) by one of two specifically instructed analysts. Colors 1 and 2 are regarded as non-infective and colors 3–5 as infective.	215	138/168 (82.1%)	15/47 (31.9%)
Soler 2007 [12]	Prospective cohort study, Spain	COPD exacerbation Hospital	Not reported 40/40 with dyspnea; 22/40 with purulent sputum; 10/40 with increased sputum production	Specimen brush	Sputum purulence was considered when patients referred to a change in the color of sputum over the past 72 hr from uncolored to yellow–green.	40	17/22 (77.3%)	1/18 (5.6%)
Soler 2012 [13]	Prospective cohort study, Spain	COPD exacerbation Hospital	Type I or II	Expectoration	Sputum was defined as ‘‘purulent’’ when patients reported a change in the color of spontaneously expectorated samples over the past 72 hr from uncolored to yellow-green.	41	12/30 (40%)	2/11 (18.2%)
Stockley 2000 [14]	Open, longitudinal study, United Kingdom	COPD exacerbation Primary care setting	Not reported 82/121 with dyspnea; 87/121 with purulent sputum; 83/121 with increased sputum production	Expectoration	A standard color chart based on neutrophil myeloperoxidase concentrations was used.	121	73/87 (83.9%)	13/34 (38.2%)
Tsimogianni 2009 [15]	Prospective cohort study, Greece	COPD exacerbation Emergency Department	Not reported 28/94 with purulent sputum	Expectoration	The purulence of the sample was judged by American Medical Technologists on site.	94	16/28 (57.4%)	20/66 (30.3%)

COPD: Chronic obstructive pulmonary disease; PPM: Potential Pathogenic Microorganisms.

Table 2. Quality appraisal of included observational studies.

References	Quality appraisal (indicators from New-Castle-Ottawa scale)									Total points
	1	2	3	4	5A	5B	6	7	8
Allegra 2005 [10]	*	*	*	*	*	*	*	*	*	9
Daniels 2010 [11]	*	*	*	–	*	*	*	*	–	7
Soler 2012 [13]	*	*	–	*	*	*	*	*	*	8
Soler 2007 [12]	*	*	–	–	*	*	*	*	*	7
Stockley 2000 [14]	*	*	*	–	*	*	*	*	*	8
Tsimogianni 2009 [15]	*	*	*	*	*	*	*	*	*	9

NR: Not reported.

1. Indicates exposed cohort truly representative.

2. Non-exposed cohort drawn from a same source.

3. Ascertainment of exposure from a secure record.

4. Outcome of interest not present at start of study.

5A. Cohorts comparable on basis of main factor.

5B. Cohorts comparable on other factors.

6. Assessment of outcome of record linkage or independent blind assessment.

7. Follow-up long enough for outcomes to occur.

8. Complete accounting for cohorts.

Figure 2. Forest plot of purulent versus mucoid sputum samples on sputum culture results.

Table 3. GRADE summary of findings.

No. of studies, design	Quality assessment						Summary of findings
	Limitations	Inconsistency	Indirectness	Imprecision	Publication bias	Upgrading	Sample size		RR, 95% CI	Quality
							Intervention	Control
PPM positive rate 6 observational studies	Moderate^a	Moderate^b	None	None	N/A	Large effect	771	321	2.14 [1.25, 3.67]	Moderate

^a Less than 50% weighed studies had 2 or more losing points in NOS.

^bI²>50%.

GRADE: Grading of Recommendations Assessment, Development and Evaluation; RR: Risk ratio; CI: Confidence interval; N/A: Not applicable; NOS: NewCastle-Ottawa scale; PPM: Potential Pathogenic Microorganisms.

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