Table 3.
Detailed characteristics of included studies considering methods of collection and analysis of saliva.
| Author, Year | Oncological Diagnosis | Type of Saliva and Method of Collection | Centrifugation and Storing | Method of Analysis | Potential Discriminant Metabolites in Saliva |
|---|---|---|---|---|---|
| Bel’skaya & Sarf, 2022 [36] | breast cancer | unstimulated whole saliva 5 mL collected by spitting into sterile polypropylene tubes; collection of saliva samples was carried out on an empty stomach after rinsing the mouth with water at 8:00–10:00 a.m. | centrifuged at 10,000× g for 10 min, biochemical analysis immediately performed without storage and freezing | StatFax 3300 semi-automatic biochemical analyser | prognostic marker: diene conjugates (level above 3.93 c.u.) |
| Bel’skaya et al., 2022 [37] | breast cancer | unstimulated whole saliva 5 mL collected by spitting into sterile polypropylene tubes; collection of saliva samples was carried out on an empty stomach after rinsing the mouth with water at 8:00–10:00 a.m. | centrifuged at 10,000× g for 10 min, biochemical analysis immediately performed without storage and freezing | StatFax 3300 semi-automatic biochemical analyser | up: total content of α-amino acids, urea; down: total protein, uric acid |
| Cavaco et al., 2018 [38] | breast cancer | unstimulated whole saliva collected in an 8–mL sterilised glass vials after rinsing the mouth with water in the morning | stored at –80 °C in aliquots of 2 mL until analysis | HS-SPME/GC-MS | Portugal: down: 3-methyl-butanoic acid, 4-methyl-pentanoic acid, phenol, acetic acid, propanoic acid, butanoic acid; India: up: acetic acid, propanoic acid, butanoic acid, 3-methyl-butanoic acid, 4-methyl-pentanoic acid down: 1,2-decanediol, pentanoic acid |
| Murata et al., 2019 [39] | breast cancer | unstimulated saliva 400 μL collected in a 50 cc polypropylene tube (a polypropylene straw 1.1 cm in diameter was used to assist the saliva collection) after rinsing the mouth with water at 9:00–11:00 a.m. | immediately stored at −80 °C until analysis | CE-TOF-MS | among 31 metabolites the top eight ranked included spermine, N1-acetylspermine, leucine, glutamine, serine, spermidine, isoleucine, and N1-acetylspermidine |
| Ragusa et al., 2021 [40] | breast cancer, lung cancer | unstimulated whole saliva 3 mL collected in a sterilised plastic vial, early in the morning, immediately transferred and centrifuged | centrifuged at 1500 rcf for 10 min, the supernatant was aliquoted in sterilised screw cap plastic vials (0.4 mL of saliva sample each) and stored at −80 °C until analysis | HPAEC-PAD | BC: up: fucose, mannose and galactose, down: glucosamine (p-value < 0.001); LC: up: fucose and mannose (p-value < 0.001), down: galactose (p-value < 0.01), and galactosamine (p-value < 0.05) |
| Sugimoto et al., 2010 [41] | breast cancer, pancreatic cancer | unstimulated whole saliva 5 mL for 5–10 min, spitted into 50 mL Falcon tubes, placed in a Styrofoam cup filled with crushed ice | centrifuged at 2600× g for 15 min at 4 °C and spun for 20 min in case of incomplete separation, transferred to two fresh tubes and frozen within 30 min | CE-TOF-MS | BC: C2H6N2, C30H62N19O2S3, taurine, C8H9N, lysine, glycerophosphocholine and C7H8O3S (p-value < 0.001), C32H48O13, C4H12N5, cadaverine, putrescine, leucine + isoleucine, tyrosine, proline, aspartic acid, glutamic acid and threonine (p-value < 0.01), C30H55N27O3S, alpha-aminobutyric acid, alanine, piperideine, phenylalanine, ethanolamine, glycine, ornithine, valine, and serine (p-value < 0.05); PC: C2H6N2, C3H7NO2, C4H12N5, C4H9NO2, C30H62N19O2S3, alpha-aminobutyric acid, alanine, putrescine, methylimidazoleacetic acid, trimethylamine, C5H14N5, taurine, C4H9N, C6H6N2O2, leucine + isoleucine, phenyloalanine, tyrosine, lysine, ethanolamine, gamma-aminobutyric acid, aspartic acid, valine, tryptophan, beta-alanine, glutamic acid, threonine, serine, glutamine, hypoxantine, choline and C5H11NO2 (p-value < 0.001), cadaverine, histidine, proline, glycine, Pro-Gly-Pro/Pro-Pro-Gly, C7H12N2O3, citrulline, carnitine, glycerophosphocholine and C7H8O3S (p-value < 0.01), C30H55N27O3S, C18H32N6O6, piperidine, ornithine, C17H26N4O5, and burimamide (p-value < 0.05) |
| Takayama et al., 2016 [42] | breast cancer | unstimulated whole saliva 1 mL collected into a tube | stored < −20 °C until analysis, centrifuged at 3000× g for 10 min after thawing | UPLC-ESI-MS/MS | up: spermine, N1-acetylspermine and N1-acetylspermidine (p-value < 0.0001), N8-acetylspermidine and N1-acetylputrescine (p-value < 0.005), N1N8-diacetylspermidine, N1N12-diacetylspermine, and cadaverine (p-value < 0.05) |
| Xavier Assad et al., 2020 [43] | breast cancer | stimulated whole saliva 5–10 mL collected with a cotton swab (Salivette®) for 2 min, placed in a plastic container and packaged in a Styrofoam box with recyclable ice packets for less than 4 h before transport and processing | centrifuged at 3000 rpm for 5 min at 8 °C, stored at −80 °C until analysis | LC-Q-TOF-MS | up: 31 metabolites, including 7 oligopeptides and 6 glycerophospholipids (PG 14:2, PA 32:1, PS 28:0, PS 40:6, PI 31:1, and PI 38:7) |
| Zhong et al., 2016 [44] | breast cancer | unstimulated whole saliva 2 mL collected at 8:30–10:30 a.m. | centrifuged at 13,500 rpm for 20 min and at 4 °C, stored at −40 °C until analysis | HILIC-UPLC-ESI-MS, RP-UPLC-ESI-MS | up: lysophosphatidylcholine (18:1, 22:6), monoacylglycerol (0:0/14:0/0:0), lysophosphatidylethanolamine (18:2/0:0), histidine, and N-acetylneuraminic acid (p-value < 0.001), lysophosphatidylcholine (16:0), phosphatidylserine (14:1/16:1) phosphatidylcholine (18:1/16:0), phenylalanine, citrulline, phosphatidylethanolamine (22:/20:4), and 4-hydroxyphenylpyruvic acid (p-value < 0.05); down: lysophosphatidylcholine (18:2) and phytosphingosine (p-value < 0.001), palmitic amide, acetylphenylalanine, and propionylcholine (p-value < 0.05) |
| Asai et al., 2018 [45] | pancreatic cancer | unstimulated whole saliva 400 µL collected in a 50 cc polypropylene tube (a polypropylene straw 1.1 cm in diameter was used to assist the saliva collection) after rinsing the mouth with water at 8:00–11:00 a.m. | immediately stored at −80 °C until analysis | CE-TOF-MS | up: spermine, N1-acetylspermidine, N1-acetylspermine, 2-aminobutanoate |
| Chen et al., 2018 [46] | gastric cancer | unstimulated whole saliva 4 mL collected after cleaning the mouth | centrifuged at 12,000 rpm for 30 min at 4 °C, 2 mL of the supernatant transferred into centrifuge tubes and stored at –70 °C | HPLC-MS, SERS | both EGC and AGC: up: taurine, glutamine, ethanolamine, histidine, alanine, glutamic acid, proline |
| Bel’skaya et al., 2020 [47] | gastric cancer, colorectal cancer | unstimulated whole saliva 2 mL collected on an empty stomach after rinsing the mouth with water at 8:00–10:00 a.m. | centrifuged at 10,000× g for 10 min, biochemical analysis immediately performed without storage and freezing | capillary gas chromatography | GC: up: acetaldehyde, acetone, methanol, ethanol, 1-propanol, 2-propanol and triene conjugates, down: diene conjugates; CRC: up: acetone, ethanol and triene conjugates, down: 1-propanol, 2-propanol, diene conjugates |
| Kuwabara et al., 2022 [48] | colorectal cancer | unstimulated saliva 400 μL collected and stored in 50 mL polypropylene tubes (a polypropylene straw 1.1 cm in diameter was used to assist the saliva collection) at 9:00–11:00 a.m. | immediately stored at −80 °C until analysis | CE-TOF-MS, LC-QQQ-MS | up: N-acetylputrescine, N1N8-diacetylspermidine, alanine, 5-oxoproline, N1-acetylspermine, N8-acetylspermidine, succinate, 5-hydroxy-4-methylpentanoate and 2-hydroxypentanoate; down: N-acetylneuraminate, hexanoate, urate, dihydroxyacetone phosphate, aspartate, and beta-alanine |
| Hershberger et al., 2021 [49] | hepatocellular carcinoma | unstimulated whole saliva collected using the DNA Genotek OMNIgene ORAL OM-505 after a standard mouth rinse | NR | GC-TOF-MS | down: acetophenone, octadecanol, lauric acid, 3-hydroxybutyric acid, threonic acid, glycerol-alpha-phosphate, butylamine, alphatocopherol |
| Bel’skaya et al., 2021 [50] | lung cancer | unstimulated whole saliva 5 mL collected by spitting into sterile polypropylene tubes; collection of saliva samples was carried out on an empty stomach after rinsing the mouth with water at 8:00–10:00 a.m. | centrifuged at 10,000× g for 10 min, biochemical analysis immediately performed without storage and freezing | StatFax 3300 semi-automatic biochemical analyser | diene conjugates, uric acid (depending on the smoking history and the severity of COPD) |
| Jiang et al., 2021 [51] | lung cancer | unstimulated whole saliva collected in SalivaGetinTM device by passive drooling at 8:30–10:30 a.m. | centrifuged at 8000× g for 10 min at 4 °C, then the resulting supernatant mixed with ACN and ultrapure water; the mixture vortexed for 10 min and centrifuged at 8000× g for 10 min at 4 °C once again and stored in the refrigerator at −80 °C until analysis | ultralow noise TELDI-MS | ELC: up: adenine, guanine, cytosine, uracil, creatinine, γ-aminobutyric acid, allysine, gentisic acid, imidazolepropionic acid, ketoleucine, N-acetylhistidine, N-acetylproline, 3-hydroxyanthranilic acid, and pyroglutamic acid; down: glycyl-phenylalanine, N-acetyltaurine, acetyl-L-glutamic acid, phenylgloxylic acid, proline, valine, arginine, serine, and xanthine |
| Takamori et al., 2022 [52] | lung cancer | unstimulated whole saliva 4–5 mL collected into 50-cc Falcon tubes kept in paper cups filled with crushed ice for 5–15 min after rinsing the mouth with water | centrifuged and immediately stored at −80 °C | CE-TOF-MS | up: diethanolamine; down: tryptophan (p-value < 0.05), choline, thymine, cytosine, phenylalanine, leucine, isoleucine, lysine, tyrosine |
| Zhang et al., 2021 [53] | papillary thyroid cancer | unstimulated whole saliva 1.5 mL collected with Salivette® polyester swabs held in mouth for 5 min after rinsing the mouth with water at 8:30–10:30 a.m. | centrifuged at 3000 rpm for 3 min and at 4 °C, stored at −35 °C until analysis | UPLC-HRMS | Down: L-valine and L-alanine (p-value < 0.001), L-phenylalanine, L-proline, L-leucine, L-tryptophan, L-threonine and L-glycine (p-value < 0.01), L-methionine, and L-isoleucine (p-value < 0.05) |
| García-Villaescusa et al., 2018 [54] | glioblastoma | unstimulated whole saliva collected in a wide-necked sterile container (“draining method”) in the morning, then transferred with a pipette to a sterile 1.5 mL Eppendorf tube | immediately stored at −80 °C until analysis | NMR spectroscopy | up: propionate and acetate; down: leucine, valine, isoleucine, alanine, ethanolamine, and sucrose |
NR, not reported; HS-SPME, headspace solid-phase microextraction; GC-MS, gas chromatography–mass spectrometry; CE-TOF-MS, capillary electrophoresis time-of-flight mass spectrometry; LC-QQQMS, liquid chromatography coupled with triple quadrupole mass spectrometry; HPAEC-PAD, high-performance anion-exchange chromatography with pulsed amperometric detection; UPLC-ESI-MS, ultra-performance liquid chromatograph electrospray ionisation–mass spectrometry; MS, mass spectrometry; LC-Q-TOF-MS, liquid chromatography coupled with quadrupole time-of-flight mass spectrometry; HILIC-UPLC-MS, ultra-performance liquid chromatography–mass spectrometry in hydrophilic interaction chromatography mode; RP-UPLC-ESI-MS, reversed-phase ultra-performance liquid chromatography electrospray ionisation–mass spectrometry; HPLC-MS, high performance liquid chromatography–mass spectrometry; SERS, surface enhanced Raman scattering; GC-TOF-MS, gas chromatography time-of-flight mass spectrometry; TELDI-MS, tip-enhanced laser desorption/ionization–mass spectrometry; UPLC-HRMS, ultra-high performance liquid chromatography–high resolution mass spectrometry; NMR spectroscopy, nuclear magnetic resonance spectroscopy; BC, breast cancer; LC, lung cancer; PC, pancreatic cancer; EGC, early gastric cancer; AGC, advanced gastric cancer; GC, gastric cancer; CRC, colorectal cancer; COPD, chronic obstructive pulmonary disease; ELC, early lung cancer.