Endoscopic laryngeal examination may reveal signs suggestive of SERD. This can vary from completely normal appearance to slight vocal cord erythema and edema, erythema of both arytenoids and posterior commissure, or increased mucosal secretion. In some advanced cases, the interarytenoid mucosa may be hypertrophic and laryngeal granulations may be present. These findings are, however, not specific and poorly correlated with other findings or with response to treatment [6]. Belfasky et al. developed the reflux finding score (RFS ) , an eight-item clinical severity scale based on findings during fiber-optic laryngoscopy [7] (Table 14.2). When evaluated in 40 patients with SERD confirmed by double-probe pH monitoring before and after treatment, the score showed excellent interobserver reproducibility and successfully documented treatment efficacy. Photographic evaluation of the larynx seems to correlate well with the RFS score and can be a useful diagnostic tool [8].

Twenty-four-hour ambulatory esophageal pH monitoring is accepted as the clinical “gold standard” for the diagnosis of GERD. In this test, a single pH probe is placed 5 cm above the lower esophageal sphincter (LES), and the exposure of the lower esophagus to acid is monitored over 24 h. It is less clear whether the technique is sensitive enough to establish an association between reflux and supraesophageal symptoms. It was hoped that dual-probe 24-h pH esophageal monitoring, using a distal and proximal site to look for the association between proximal reflux and pharyngolaryngeal manifestations, would be more sensitive to diagnose SERD. However, proximal pH recording has very good specificity (91%) but poor sensitivity (55%) for identifying abnormal proximal acid reflux, and a negative test does not exclude proximal reflux [9]. Another option is pharyngeal pH monitoring , in which the sensor is placed above the UES. Although some exposure of the pharynx to acid occurs in normal individuals, exposure time of more than 18% is considered pathological [10]. The poor correlation of proximal and distal acid events detected by dual-probe monitoring may be partly explained by the refluxate becoming less acidic by the time it reaches the proximal esophagus. These so-called weekly acidic events cannot be detected by a conventional pH monitoring but they are detected by a combination of pH and impedance monitoring.

Impedance monitoring (MII) uses the change in electrical conductivity to measure passage of refluxate near the probe, as well as the proximal extent of the refluxate. Simultaneous intraesophageal MII-pH detects reflux by impedance and characterizes it by pH (i.e., acid if pH below 4 and nonacid if pH above 4) [11].

When comparing a combination of RSI and RFS to 24-h multichannel intraluminal impedance (MII) pH monitoring in 58 patients with symptoms suggestive of SERD, Wan et al. found a better response to treatment in the group that was diagnosed by (MII) pH monitoring , reflecting the better diagnostic accuracy of the impedance monitoring over clinical scores [12].

The traditional cutoff of pH <4 for SERD could actually underestimate the presence of clinically significant reflux. Indeed if the cutoff is changed to pH 5.5 the correlation between distal and proximal reflux events improves [13]. In a study of 27 patients refractory to treatment with symptoms of SERD, pH impedance was measured before and after treatment, along with a symptom score, and there was no difference between the study and control groups. Pharyngeal reflux episodes detected by pH impedance were very rare and their presence did not predict the response to an 8-week double-dose PPI therapy . The conclusion was that in a population of patients refractory to full-dose PPI treatment the likelihood of SERD is low and other causes of the symptoms should be searched [14].

Another diagnostic method is the pH device for detection of liquid and aerosolized droplets in the oropharynx (the Dx–pH Measurement System [Dx–pH]). The probe is located in the oropharynx, behind the uvula, and is able to measure pH in either liquid or aerosolized droplets. In 7.8% of 660 episodes of pH <4 at the distal esophagus there was also a Dx–pH event. All events were preceded by and sequential to esophageal pH events. The investigators suggested using pH drops of >3 standard deviation from a baseline to define an event of SERD, rather than looking only at events of pH <4 [15]. In another study, however, Dx–pH Measurement results did not predict response to PPI treatment [16].

Salivary pepsin has been suggested as a marker of reflux but it had a sensitivity of 78% and specificity of 53% for predicting a high RFS [17].