DATA SOURCES: PubMed, Scopus, Web of Science, Embase, and Google Scholar databases were searched to identify studies published between December 1, 2019, and June 23, 2020, without language restrictions. There was no restriction on the study design; therefore, observational studies, clinical trials, and case series were included. In addition, preprints were considered if data of interest were reported.

REVIEW METHODS: Two authors independently screened articles for eligibility. A random effects model was used to estimate the pooled prevalence with 95% CIs. Quality assessment was done with critical appraisal tools of the Joanna Briggs Institute. The robustness of the pooled estimates was checked by subgroup and sensitivity analyses.

RESULTS: Fifty-nine studies were included (N = 29,349 patients, 64.4% female). The pooled prevalence of taste disorders in patients with COVID-19 was 48.1% (95% CI, 41.3%-54.8%). The prevalence of taste disorders in studies with objective assessments was higher as compared with subjective assessments (59.2% vs 47.3%). The disorders were observed in 55.2% of European patients; 61.0%, North American; 27.1%, Asian; 29.5%, South American; and 25.0%, Australian. Ageusia, hypogeusia, and dysgeusia were detected in 28.0%, 33.5%, and 41.3% of patients with COVID-19. We identified 91.5% of the included studies as high quality.

OBJECTIVES: To assess the effects of interventions for the management of patients with taste disturbances.

SEARCH METHODS: We searched the Cochrane Oral Health Group Trials Register (to 5 March 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2014), MEDLINE via OVID (1948 to 5 March 2014), EMBASE via OVID (1980 to 5 March 2014), CINAHL via EBSCO (1980 to 5 March 2014) and AMED via OVID (1985 to 5 March 2014). We also searched the relevant clinical trial registries and conference proceedings from the International Association of Dental Research/American Association of Dental Research (to 5 March 2014), Association for Research in Otolaryngology (to 5 March 2014), the US National Institutes of Health Trials Register (to 5 March 2014), metaRegister of Controlled Trials (mRCT) (to 5 March 2014), World Health Organization's International Clinical Trials Registry Platform (WHO ICTRP) (to 5 March 2014) and International Federation of Pharmaceutical Manufacturers and Associations (IFPMA) Clinical Trials Portal (to 5 March 2014).

SELECTION CRITERIA: We included all randomised controlled trials (RCTs) comparing any pharmacological agent with a control intervention or any non-pharmacological agent with a control intervention. We also included cross-over trials in the review.

DATA COLLECTION AND ANALYSIS: Two authors independently, and in duplicate, assessed the quality of trials and extracted data. Wherever possible, we contacted study authors for additional information. We collected adverse events information from the trials.

MAIN RESULTS: We included nine trials (seven parallel and two cross-over RCTs) with 566 participants. We assessed three trials (33.3%) as having a low risk of bias, four trials (44.5%) at high risk of bias and two trials (22.2%) as having an unclear risk of bias. We only included studies on taste disorders in this review that were either idiopathic, or resulting from zinc deficiency or chronic renal failure.Of these, eight trials with 529 people compared zinc supplements to placebo for patients with taste disorders. The participants in two trials were children and adolescents with respective mean ages of 10 and 11.2 years and the other six trials had adult participants. Out of these eight, two trials assessed the patient reported outcome for improvement in taste acuity using zinc supplements (RR 1.45, 95% CI 1.0 to 2.1; very low quality evidence). We included three trials in the meta-analysis for overall taste improvement (effect size 0.44, 95% CI 0.23 to 0.65; moderate quality evidence). Two other trials described the results as taste acuity improvement and we conducted subgroup analyses due to clinical heterogeneity. One trial described the results as taste recognition improvement for each taste sensation and we analysed this separately. We also analysed one cross-over trial separately using the first half of the results. None of the zinc trials tested taste discrimination. Only one trial tested taste discrimination using acupuncture (effect size 2.80, 95% CI -1.18 to 6.78; low quality evidence).Out of the eight trials using zinc supplementation, four reported adverse events like eczema, nausea, abdominal pain, diarrhoea, constipation, decrease in blood iron, increase in blood alkaline phosphatase, and minor increase in blood triglycerides. No adverse events were reported in the acupuncture trial.None of the included trials could be included in the meta-analysis for health-related quality of life in taste disorder patients.

METHODS: The degree of marbling was determined by using an established combined camera-image analysis technique while instrumental texture determination was carried out by using Warner-Bratzler shear force analysis. Sensory evaluation of the beef steaks was performed following a quantitative descriptive analysis incorporating 10 trained consumer panelists.

RESULTS: Wagyu was found to possess the highest (p<0.05) percentage of IMF at 33.90% and the lowest shear force (raw = 5.61 N/mm2; cooked = 14.72 N/mm2) followed by Angus (20.87%), Brahman (12.17%), and KK (p<0.05, 6.86%). The difference in sensory properties of the four steaks was evident, with Wagyu appearing to be highly correlated with most sensory attributes measured namely sustained buttery, tooth-packing, chewiness, juiciness, tenderness, mouthfeel, oiliness, and overall acceptability. The Malaysian local beef, KK was found to be less acceptable (p<0.05), although most of its sensory attributes were found similar (p>0.05) in appearance, aroma, texture, juiciness, and flavour to the cooked steak from Angus and Brahman.