Performances of single tube nested polymerase chain reaction and GeneXpert ultra on Formalin fixed paraffin embedded tissues in the diagnosis of tuberculous spondylodiscitis.

INTRODUCTION: Tuberculous Spondylodiscitis is the most common form of musculoskeletal tuberculosis. Molecular techniques on fresh tissues are proved to improve the diagnosis of tuberculous spondylodiscitis and to allow a rapid diagnosis to initiate the treatment and prevent neurological complications. OBJECTIVES: The objective of the present study was to assess the diagnostic performances of single tube nested PCR and GeneXpert ultra in the diagnosis of tuberculous spondylodiscitis on formalin fixed paraffin embedded tissues. METHODS: This study included 63 tuberculous spondylodiscitis cases collected from June 2014 to January 2020 and corresponding to 27 definite tuberculous spondylodiscitis with positive microbiology, and 36 probable tuberculous spondylodiscitis, with histopathological, clinical and radiological findings consistent with tuberculous spondylodiscitis but with negative microbiology. The sensitivity, specificity, positive predictive value and negative predictive value of nested PCR and GeneXpert ultra were determined with reference to microbiology. RESULTS: Nested PCR was positive in 47 (75%) cases: 26/27 definite tuberculous spondylodiscitis and 21/36 probable tuberculous spondylodiscitis. GeneXpert ultra was positive in only 6 (10%) cases corresponding to definite tuberculous spondylodiscitis. The sensitivity, specificity, positive predictive value and negative predictive value of nested PCR on formalin fixed paraffin embedded tissues were 96%, 100%, 100%, 83% respectively. For GeneXpert ultra, these rates were 22%, 100%, 100% and 25% respectively. CONCLUSION: Nested PCR and GeneXpert ultra on formalin fixed paraffin embedded tissues are useful tools for the diagnosis of tuberculous spondylodiscitis, especially for cases where microbiological investigations were not carried out. Both techniques have excellent specificity but single tube nested PCR is more sensitive. Key Points • Molecular techniques are routinely performed on fresh tissues • GeneXpert and nested PCR on formalin fixed paraffin embedded tissues are reliable for the diagnosis of tuberculous spondylodiscitis • Nested PCR is more sensitive than Genexpert for diagnosing tuberculous spondylodiscitis.

Performance of GeneXpert ultra in the diagnosis of Tuberculous Cervical lymphadenitis in formalin fixed paraffin embedded tissues.

The diagnosis of Tuberculous Cervical lymphadenitis (TCL) is challenging. The present study aimed to assess the performance of GeneXpert ultra (GXu) in the diagnosis of TCL on Formalin Fixed, Paraffin Embedded Tissues (FFPET). This study included 35 TCL cases confirmed by positive microbiology and/or positive GXu on Fresh Tissues (FT). The diagnostic performance parameters of GXu on FFPET were determined with reference to microbiology (positive Ziehl Neelsen and/or positive culture) and with reference to positive microbiology and/or positive GXu on FT. The GXu on FFPET was positive in 26/35 (74%) cases. With reference to positive ZN and or culture, the sensitivity, specificity, positive predictive value, and negative predictive value of GXu on FFPET were 63%, 100%, 100% and 71% respectively. With reference to positive microbiology and/or positive GXu on FT, these rates were 74%, 100%, 100% and 40% respectively. GXu on FFPET is a reliable tool for the detection of Mycobacterium tuberculosis complex particularly for cases where microbiological investigations have not been performed.

[Lafora disease: histopathological study of axillary cutaneous biopsy]. / Maladie de Lafora : étude histopathologique d'une biopsie cutanée axillaire.

Lafora body disease is a common and severe form of progressive myoclonic epilepsy. It is an autosomal recessive disorder with a gene locus recently mapped to chromosome 6q23-27. The disease presents between the age of 10 and 18 years with generalised seizures followed by myoclunus. Intellectual deterioration occurs early and progresses to dementia. The diagnosis must be usually confirmed by demonstrating Lafora bodies. The practical procedure is the axillary skin biopsy that shows PAS positive inclusion in the cells of the sweet ducts. We present a case of Lafora disease discovered in a 26-year-old man. Moreover, we emphasize on the diagnosis difficulties of this disease.