Atypical Pathogen Distribution in Chinese Hospitalized AECOPD Patients: A Multicenter Cross-Sectional Study

Figures & data

Table 1 The Result Determination Criteria of PCR

Result	Sample	Internal Reference	Negative Control
Negative	No amplification	Detectable	Negative
Positive	Amplification Cp < 37		Negative

Notes: If the internal reference is not detected, it indicates PCR failure; If the negative control is positive, it indicates PCR contamination.

Table 2 General Demographic Data

Clinical Characteristics
Number of patients	145
Age in years(Mean±SD)	74.35±10.07
Gender (male)	70.34%
BMI(kg/m^2)(Mean±SD)	22.58±4.12
Smoker	66.21%
Spirometry(post)
FEV1% pred(Mean±SD)	41.81±19.31
FVC % pred(Mean±SD)	59.57±20.21
FEV1/FVC(Mean±SD)	51.75±14.35
Comorbidities	63.45%

Table 3 The Specific Results of Atypical Pathogens Detected by Various Methods

Mycoplasma pneumoniae
Detection method	Positive rate (positive/total)
Passive agglutination	20.00%(29/145)
IgM(enzyme immunoassay)	2.75%(4/145)
PCR(sputum)	1.75%(2/114)
Total	20.69%(30/145)
Chlamydia pneumoniae
Detection method	Positive rate (positive/total)
Microimmunofluorescence assay(MIF)	29.66%(43/145)
PCR(sputum)	0%(0/114)
Total	29.66%(43/145)
Legionella pneumophila
Detection method	Positive rate (positive/total)
Indirect fluorescent	10.34%(15/145)
IgM(ELISA)	0.69%(1/145)
PCR(sputum)	0%(0/115)
Urinary Antigen	0%(0/145)
Total	10.34%(15/145)

Table 4 Frequency of the Various Legionella pneumophila Serotype Identified in the 11 Hospital Admissions

Legionella pneumophila	N(%)
Legionella pneumophila-6	9 (60.00%)
Legionella pneumophila-14	5 (33.33%)
Legionella pneumophila-1	4 (26.67%)
Legionella pneumophila-7	3 (20.00%)
Legionella pneumophila-8	3 (20.00%)
Legionella pneumophila-10	3 (20.00%)
Legionella pneumophila-12	3 (20.00%)
Legionella pneumophila-4	2 (13.33%)
Legionella pneumophila-11	2 (13.33%)
Legionella pneumophila-2	1 (6.67%)
Legionella pneumophila-5	1 (6.67%)
Two serotypes positive	3 (20.00%)
≧three serotypes positive	6 (40.00%)

Table 5 The Clinical Characteristics of Patients Tested Positive for the Three Atypical Pathogens

Characteristics	Mycoplasma pneumoniae-Positive (n=30)	Mycoplasma pneumoniae-Negetive (n=115)	P value	Chlamydia pneumoniae-Positive (n=43)	Chlamydia pneumoniae-Negetive (n=102)	P value	Legionella pneumophila-Positive (n=15)	Legionella pneumophila-Negetive (n=130)	P value
Age (years)	76.10±9.32	73.89±10.25	0.280	74.09±8.90	74.46±10.57	0.844	74.60±9.07	74.32±10.21	0.919
Sex, Males:Female	23:7	79:36	0.395	29:14	73:29	0.619	10:15	92:130	0.742
BMI (kg/m^2)	22.92±4.52	22.48±4.02	0.236	21.78±3.97	22.92±4.16	0.135	22.81±3.41	22.55±4.20	0.823
Height(cm)	161.48±31.82	164.42±17.56	0.221	166.02±7.13	166.20±8.42	0.903	167.07±6.58	166.04±8.20	0.641
Vital signs
Maximum body temperature in hospital(°C)	37.38±0.90	37.01±0.57	0.001**	37.09±0.75	37.09±0.63	0.988	37.19±0.65	37.08±0.67	0.552
Pulse(Mean±SD)	90.80±14.59	88.91±13.57	0.374	89.26±14.60	89.32±13.46	0.755	92.87±15.62	88.89±13.53	0.291
Rate(Mean±SD)	20.93±2.12	21.15±2.706	0.319	21.21±2.69	21.06±2.56	0.752	21.00±2.04	21.12±2.65	0.875
Proportion of patients admitted to intensive care unit	13.33%	15.65%	0.753	18.60%	13.73%	0.454	13.33%	15.38%	0.834
Days from onset to admission	8.67±7.25	14.64±22.15	0.066	13.14±13.81	13.49±22.31	0.924	9.93±7.34	13.79±21.06	0.484
Smokers	66.67%	66.96%	0.976	65.11%	66.67%	0.857	66.67%	66.15%	0.968
Tobacco quantity(pack per year)	52.02±32.78	46.51±31.16	0.689	62.33±40.11	44.10±25.60	0.036*	44.11±22.52	50.10±32.41	0.591
Comorbidities	66.67%	62.61%	0.620	80.95%	57.43%	0.007**	46.67%	66.41%	0.131
Number of acute exacerbations in the past year	1.14±1.19	1.55±1.19	0.735	1.28±1.24	1.54±1.17	0.276	1.31±1.11	1.48±1.21	0.618
Number of acute exacerbations in the past year≥2	40.00%	46.09%	0.247	34.21%	55.91%	0.024*	38.46%	50.85%	0.397
Spirometry(post)
FEV1% pred	36.43±19.67	43.84±18.96	0.649	38.81±15.86	43.39±19.45	0.376	53.56±27.13	40.60±18.20	0.091
FVC % pred	51.90±18.86	62.12±20.15	0.880	60.34±17.92	59.35±20.96	0.863	65.05±27.36	59.07±19.63	0.491
FEV1/FVC	49.15±16.79	52.84±13.24	0.244	51.72±11.22	51.76±15.21	0.993	62.95±3.30	50.80±14.54	0.000**
Proportion of long-term inhaled or oral glucocorticoid therapy	30.00%	30.43%	0.963	32.35%	35.29%	0.645	26.67%	30.77%	0.743
CAT	25.53±6.51	25.98±6.68	0.601	25.21±7.03	26.20±6.49	0.422	28.13±4.07	25.65±6.85	0.051
mMRC	3.10±0.10	2.91±1.11	0.262	2.98±1.02	2.94±1.11	0.861	2.80±0.86	2.97±1.11	0.570
Blood gas
PH	7.40±0.05	7.40±0.07	0.435	7.41±0.06	7.40±0.07	0.399	7.41±0.05	7.40±0.07	0.630
PaCO2 in mmHg	47.72±15.75	49.88±15.50	0.933	48.56±15.86	49.84±15.44	0.664	43.49±14.87	50.15±15.51	0.130
HCO3^− in mmol/L	29.92±6.09	31.64±16.87	0.440	29.79±7.02	30.21±6.74	0.752	26.33±5.63	30.47±6.82	0.044*
PaO2/FiO2	293.28±117.16	288.28±98.19	0.537	229.20±124.89	268.42±118.95	0.127	179.27±120.90	261.17±120.41	0.068
Lactate(mol/L)	1.15±0.52	1.35±0.87	0.385	1.23±0.66	4.16±20.08	0.428	1.10±0.33	3.30±16.84	0.714
Routine blood test
White blood cell (*10^9/L)	8.12±3.62	13.78±41.99	0.302	8.59±3.80	9.96±10.70	0.427	8.07±3.24	13.12±39.50	0.622
Neutrophil(*10^9/L)	6.31±3.07	7.15±5.56	0.306	7.72±7.74	6.67±3.56	0.269	5.82±2.70	7.12±5.35	0.358
Neutrophilt(%)	74.05±14.29	73.28±14.03	0.789	72.00±14.12	74.04±14.04	0.43	72.21±14.95	73.58±13.99	0.721
Eosinophilst(%)	3.43±7.91	1.40±1.85	0.001**	1.86±1.88	1.81±4.64	0.955	5.27±10.88	1.42±1.86	0.192
Red blood cell(*10^12/L)	4.40±0.72	4.89±0.85	0.813	4.42±0.76	4.42±0.74	0.982	4.03±1.41	4.43±0.73	0.289
Hemoglobin(g/L)	133.04±20.66	132.61±24.64	0.648	132.70±19.04	132.70±25.72	1.00	125.53±28.11	133.55±23.31	0.220
Hematocrit(%)	40.58±8.08	40.67±8.07	0.864	40.30±8.29	40.74±8.06	0.779	37.57±9.27	40.97±7.91	0.138
Hematocrit>50%	6.67%	9.57%	0.835	13.15%	8.42%	0.406	0%	10.92%	0.193
C-reactive protein(mg/dl)	35.74±64.95	25.48±31.42	0.048*	23.06±26.04	30.19±46.51	0.432	33.79±30.94	27.52±40.98	0.694
PCT(ng/mL)	3.21±11.00	0.21±0.95	0.000**	1.43±7.65	0.69±4.07	0.507	4.65±14.54	0.56±3.51	0.398
ALT(U/L)	17.91±12.23	29.85±63.77	0.217	20.32±17.21	30.37±67.06	0.352	17.02±10.33	28.63±60.32	0.475
AST(U/L)	23.25±11.38	28.79±28.30	0.126	27.53±32.43	27.73±22.62	0.967	24.38±13.61	28.01±26.81	0.632
ALB(g/L)	35.18±6.17	38.57±24.73	0.623	41.58±40.76	36.40±5.73	0.453	36.75±7.01	35.96±5.91	0.680
LDH(U/L)	172.72±52.54	226.12±116.33	0.051	223.19±116.33	19.57±105.07	0.291	169.09±44.21	210.79±113.43	0.231
BUN(mmol/L)	7.01±2.79	7.32±4.15	0.480	8.19±5.64	6.78±2.51	0.135	6.94±2.26	7.30±4.07	0.777
Na(mmol/L)	140.30±4.97	139.59±5.27	0.669	139.44±6.88	139.86±4.35	0.666	140.46±4.50	139.66±5.28	0.583
K(mmol/L)	4.14±0.55	4.04±0.54	0.597	3.98±0.59	4.10±0.52	0.267	4.02±0.42	4.07±0.55	0.755
Cl(mmol/L)	100.44±3.75	99.06±7.34	0.045*	99.07±9.76	99.46±5.08	0.810	100.24±4.73	99.24±6.97	0.604
Fasting blood glucose (mmol/L)	6.03±1.82	7.84±8.59	0.173	7.31±3.56	7.56±8.94	0.873	6.15±1.66	7.61±7.91	0.565
CK(U/L)	59.33±34.12	140.20±527.88	0.239	70.65±46.69	73.54±80.34	0.853	64.67±46.47	73.38±72.15	0.725
D-D(ug/L)	1.70±3.45	1.39±2.76	0.353	1.34±1.98	1.50±3.22	0.776	2.72±4.67	1.32±2.62	0.112
Mechanical ventilation(%)	16.67%	26.09%	0.283	28.21%	24.74%	0.676	20.00%	26.45%	0.590
Duration of hospitalization (days)	16.07±10.48	13.89±8.14	0.115	13.53±6.55	14.72±9.48	0.455	16.80±10.70	14.09±8.44	0.254
Improvement rate on the third day#	93.33%	88.70%	0.619	92.86%	91.00%	0.717	100%	90.55%	0.213

Notes: *p<0.05; **p<0.01; ^#Improvement refers to When the patients meet the following conditions on day 3: symptoms and signs of AECOPD were improved and no new symptoms appeared compared with baseline, lung infiltration shadow absorption or no obvious deterioration, and laboratory indicators related to infection were improved (including peripheral blood leukocyte count, peripheral blood neutrophil percentage, CRP and PCT, etc).

Table 6 The Sensitivity, Specificity, False Positivity and False Negativity of Each Pathogen Detection Methods

Atypical Pathogens	Mycoplasma pneumonia^Citation8,Citation10,Citation20			Chlamydia pneumonia,^Citation15,Citation16		Legionella pneumophila^Citation9,Citation18
	Passive Agglutination Method^Citation8*	IgM^Citation20 #	PCR^Citation10,Citation20	Microimmunofluorescence Assay, MIF^Citation15,Citation16*	PCR^Citation15,Citation16*	Indirect Fluorescent Antibodies^Citation18	IgM^Citation9	PCR^Citation18	Urine Antigen^Citation18
Sensitivity	100%^Citation8*	7.4%^Citation20 #	0%^Citation10** 40.7%^Citation20 #	16.5%^Citation15* 82%^Citation16*	15.00%^Citation15* 71%^Citation16*	40–80%	92.3%	30–100%	70–90%
Specificity	95.6%^Citation8*	94.9%^Citation20 #	95.2%^Citation10** 88.8%^Citation20 #	94.55%^Citation15* 40%^Citation16*	81.82%^Citation15* 97%^Citation16*	95–100%	100%	95–100%	95–100%
PPV	–	28.6%^Citation20 #	0^Citation10** 50%^Citation20 #	68.42%^Citation15* 34%^Citation16*	37.5%^Citation15* 90%^Citation16*	–	–	–	–
NPV	–	78.8%^Citation20 #	85.1%^Citation10** 84.5%^Citation20 #	60.82%^Citation15* 85%^Citation16*	56.96%^Citation15* 90%^Citation16*	–			–

Notes: *With clinically diagnosed cases as reference standard; ^#With a fourfold or greater increase of IgG antibody titers of paired sera as reference standard; **With IgM positivity as reference standard.

Abbreviations: PPV, positive predictive values; NPV, negative predictive values; PLR, positive likelihood ratio.

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