Table 2 Meta-regression analysis coefficients for TNF-α levels

Sample size

–

0.01095

0.00551

1.99000

0.05300

−0.00015

0.02205

BMI

–

0.96000

0.34400

−0.25631

0.72067

0.96000

0.34400

Age

–

0.79053

0.32494

2.43000

0.01900

0.13607

1.44500

NOS

–

−0.57894

0.30767

−1.88000

0.06600

−1.19861

0.04073

Development

–

−1.83779

1.08681

−1.69000

0.09800

−4.02674

0.35115

regions

America

−1.15015

1.41992

−0.81000

0.42200

−4.01001

1.70972

Asia

−0.18814

1.01291

−0.19000

0.85300

−2.22825

1.85196

Europe

–

–

–

–

–

–

Severity

All

−0.18343

1.27352

−0.14000

0.88600

−2.74843

2.38157

mild

−0.45801

1.38464

−0.33000

0.74200

−3.24681

2.33079

moderate

−0.81363

1.51188

−0.54000

0.59300

−3.85871

2.23145

moderate to severe

−0.20049

1.32277

−0.15000

0.88000

−2.86469

2.46371

severe

−0.29741

1.21544

−0.24000

0.80800

−2.74542

2.15061

mild to moderate

–

–

–

–

–

–

Method

CLIA

0.21982

2.64027

0.08000

0.93400

−5.09796

5.53759

ELISA

−3.70431

1.97035

−1.88000

0.06700

−7.67281

0.26418

ECLIA

–

–

–

–

–

–

Specimen

Exhaled breath condensate

2.90545

2.75026

1.06000

0.29600

−2.63385

8.44475

PBMC

−3.25580

3.41251

−0.95000

0.34500

−10.12894

3.61734

Pharyngeal lavage

0.79203

2.68878

0.29000

0.77000

−4.62345

6.20751

Plasma

−0.27113

2.43064

−0.11000

0.91200

−5.16669

4.62444

Saliva

0.32275

2.90335

0.11000

0.91200

−5.52490

6.17041

Serum

0.60803

2.45687

0.25000

0.80600

−4.34035

5.55641

Gingival crevicular fluid

–

–

–

–

–

–

Gender

–

−0.18789

0.35411

−0.53000

0.59800

−0.90109

0.52531

All

–

9.10716

4.37081

2.08000

0.04300

0.30389

17.91043