Interexaminer agreement dental caries epidemiological surveys: the importance of disease prevalence in the sample

Objective: To identify desirable characteristics, including different sample sizes and dental caries prevalences, in virtual samples that allow, at the same time, higher values of general agreement percentage (GPA) and Kappa coefficient (κ), under a low confidence interval (CI), in reproducibility studies. Method: A total of 384 statistical simulations of inter-examiner calibration, varying sample size (12, 15, 20, 60, 200 and 500 individuals), caries prevalence (30, 50, 60 and 90%) and percentages of positive (PA) and negative (NA) agreement (30, 50, 60 and 90%) were undertaken. GPA and κ were used to measure reproducibility and define deviation between them. Results: The sample of 60 individuals, under caries prevalence of 50%, PA and NA of 90%, presented a GPA and Kappa values of 90 and 80%, respectively, a relative small confidence interval (95%CI 0.65 - 0.95) and a GPA/Kappa deviation of 10.00. Conclusion: A virtual sample of 60 individuals, under caries prevalence of 50%, seems feasible to produce a satisfactory interexaminer agreement at epidemiological conditions. However, epidemiological studies to corroborate or refute this assertion are necessary.

Identification and Determination of Oxytetracycline, Tiamulin, Lincomycin, and Spectinomycin in Veterinary Preparations by Thin-Layer Chromatography/Densitometry

A thin-layer chromatographic/densitometric method was developed for the identification and quantitation of oxytetracycline, tiamulin, lincomycin, and spectinomycin in veterinary preparations. Silica gel-coated thin layer chromatography plates and 2 mobile phases were used to separate these constituents. The appropriate compositions of the suitable mobile phases were established: 10% citric acid solution–n-hexane–ethanol (80 + 1 + 1, v/v) and n–butanol–ethanol–chloroform– 25% ammonia (4 + 5 + 2 + 5, v/v). Along with Rf values and spot colors, direct UV and visual densitometric measurements were used for identification. Similar measuring ranges were used for quantitative analysis to obtain repeatable and reliable results for the preparations examined. The results of the quantitative analysis are characterized by a small confidence interval and are close to the declared contents of active constituents: oxytetracycline 30.01 ± 0.38 g at λ = 350 nm and 30.24 ± 0.86 g at λ = 430 nm; tiamulin, 10.19 ± 0.86 g at λ = 450 nm; lincomycin, 2.27 ± 0.08 g at λ = 278 nm; and spectinomycin, 2.18 ± 0.07 g at λ = 421 nm. The recoveries for all antibiotics ranged from 100.01 to 102.54%.