Laryngopharyngeal reflux comes with a different salivary microbiome - which is not yet a test

Design

Prospective controlled study with 16S rRNA sequencing and salivary enzyme assays

Population

67 patients with laryngopharyngeal reflux confirmed on 24-hour impedance-pH testing and 44 asymptomatic controls

Primary outcome

Salivary microbiome composition and digestive enzyme concentrations

Effect

Reduced Shannon diversity at family and genus level (P < 0.006), distinct beta diversity (PERMANOVA P at or below 0.005), raised elastase and salivary pH in the reflux group

Sixty-seven patients with laryngopharyngeal reflux confirmed on 24-hour hypopharyngeal-oesophageal multichannel intraluminal impedance-pH testing gave saliva samples alongside 44 asymptomatic controls, analysed for digestive enzymes and by 16S ribosomal RNA sequencing.

The reflux group had higher salivary elastase, higher salivary pH and lower cholesterol. Microbially, alpha diversity was reduced at family and genus level (Shannon index, P < 0.006) and community composition differed on beta diversity measures (PERMANOVA, P at or below 0.005). Specific taxa moved: Actinomyces and Abiotrophia raised, Oribacterium and the Eubacterium nodatum group depleted, with Streptococcus species modulated. Elastase, trypsin and bile salts each correlated with the abundance of particular organisms.

The authors describe this as preliminary and that is the right word. It is a controlled comparison, not a diagnostic study: no threshold, no sensitivity, no test characteristics, and a group defined by impedance-pH testing that most patients with reflux symptoms never receive. Its value is conceptual - the notion that laryngopharyngeal reflux is a chemical injury alone is harder to hold when the enzyme profile and the microbial community both shift together. Nothing in it justifies ordering a salivary panel, and nothing in it says whether the microbiome change is a cause, a consequence, or a marker of the same underlying process.

• Do not order salivary pepsin or microbiome panels on the strength of this; no diagnostic thresholds were derived.
• Continue to diagnose laryngopharyngeal reflux on symptoms, signs and, where available, impedance-pH testing.
• Note that the control group was asymptomatic volunteers, not patients with other laryngeal disease - the harder comparison.
• The enzyme findings, particularly elastase, are the more immediately testable part of this work.
• Treat causal direction as entirely open.

The statistics, in plain English

Alpha diversity measures how varied the community is within one person and beta diversity how different people are from each other; both moved, which is more convincing than either alone. But with 67 patients and 44 controls, differential abundance analyses across many taxa carry a real risk of chance findings, and the P values quoted are for the diversity indices rather than for each individual organism. A significant difference between groups says nothing about whether the measure could separate an individual patient from a control.

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