Comparison of diagnostic tests for suspected cow's milk allergy in children with atopic dermatitis.

BACKGROUND: Atopic dermatitis (AD) is a chronic inflammatory skin disease. A third of pediatric AD patients have also food allergy. Although food challenge test is gold standard test for the diagnosis of food allergies, they should be administered by experienced physicians, considering that the test is time-consuming and carries some risks. Documentation of the efficacies of specific IgE (sIgE), skin prick test (SPT), and atopy patch test (APT) are important for determining the necessity of oral food challenge tests(OFC). METHODS: Fifty-three AD patients with suspected cow's milk allergy (CMA) were included in our study. Diet-related questions were asked to the patients. Blood samples were taken for measurement of total blood count, total IgE, and milk sIgE. OFC, SPT, and APT were performed using pasteurized cow milk. RESULTS: The mean age of the study population was 1.4±0.8 years, and the male:female ratio was 1.12. Cow milk allergy was detected in 45.3% of the patients after OFC. A comparison between CMA(+) and CMA(-) patients revealed no significant difference in sIgE positivity (P=0.940), but there was a significant difference in SPT (P=0.000) and APT (P=0.001) positivity. When our study group was divided into immediate reaction, delayed onset reaction, and not reactive subgroups after OFC, efficacy of SPT was more prominent in immediate reaction subgroup while APT was more efficient in delayed reaction subgroup. CONCLUSIONS: Our study showed that using SPT test with APT test in allergic reactions with IgE and other mechanisms such as AD will increase the diagnostic yield, thereby reducing the need for OFC.

[The use of polymerase chain reaction in laboratory diagnosis of dermatophytosis]. / Dermatofi tozlarin laboratuvar tanisinda polimeraz zincir reaksiyonunun kullanilmasi.

Dermatophytes are among the common causes of fungal infections in the community. Classical diagnostic tests for dermatophytosis have some disadvantages such as failure of direct microscopy in species differentiation and culture methods being time consuming and having low sensitivity. The aim of this study was to investigate the performance of polymerase chain reaction (PCR) in the identification of dermatophytes directly from the clinical samples and the cultures. A total of 123 samples that comprise 63 skin and 60 nail scrapings obtained from 110 patients (69 female, 41 male; age range: 4-82 years) who were prediagnosed as dermatophytosis, were included in the study. Samples were examined with routine direct microscopy, culture and two different nested PCR (nPCR) protocols. The first was a pan-dermatophyte nPCR protocol targeting chitin synthase gene (CHS-1) of dermatophytes and the second was a nPCR protocol which targets specific ITS-1 genes of Trichophyton rubrum and T.mentagrophytes. Similar PCR methods were also applied to cultivated strains. Sequence analysis was performed for the samples that yielded positive results in pan-dermatophyte nPCR and negative results in T.rubrum/T.mentagrophytes - specific nPCR. Hyphae and/or spore structures were observed in 62 (50%) samples with direct microscopic examination and dermatophytes were isolated in 30 (24%) samples. Twenty-eight of the isolates grown in culture were identified as T.rubrum, and two as T.mentagrophytes with T.rubrum/T.mentagrophytes-specific nPCR protocol. In direct application, 67 (55%) of the clinical samples were found positive with pan-dermatophyte nPCR and 65 (53%) were positive with T.rubrum/T.mentagrophytes-specific nPCR. Samples which were negative in direct microscopic examination were also negative in culture. Nine of them were found positive with pan-dermatophyte nPCR and eight were positive with T.rubrum/T.mentagrophytes-specific nPCR. Two of the 30 samples which were positive in culture were negative in direct pan-dermatophyte nPCR, and one of them was negative in T.rubrum/T. mentagrophytes-specific nPCR. Three samples which were positive by pan-dermatophyte nPCR, gave negative result with T.rubrum/T.mentagrophytes-specific nPCR. Sequence analysis was performed for these three samples and all were identified as T.rubrum. In evaluation of concordance between the methods, the agreement of direct microscopy and culture was moderate (kappa value; κ= 0.48), the agreement of direct microscopy and both protocols of nPCR was high (κ= 0.78) and the agreement of both nPCR protocols with each other was excellent (κ= 0.93). Our data indicated that two different nPCR methods used for the laboratory diagnosis of dermatophytosis yielded higher positivity in less time than the culture method. In conclusion, nPCR was considered to be useful in identification of dermatophytosis from either direct clinical samples or culture-isolated strains.