A kit for detecting a micro-RNA of interest in at least one sample extracted from a body fluid, comprising: - at least one device including a housing casing in which at least one housing seat is obtained for said at least one sample, and at least one opening through which said housing seat is accessible from the outside; - at least one container means for said at least one sample, said at least one container means being insertable/disconnectable in/from said housing seat through said at least one opening; - means for administering at least one molecular marker in said at least one container means, said at least one molecular marker being associable with said micro-RNA of interest in said sample; - at least one oligonucleotide probe, each oligonucleotide probe being set to establish a specific bond with a respective complementary sequence of nucleotides present in a strand of said micro-RNA of interest, said at least one oligonucleotide probe provided in said administration means or in said at least one container means; - at least one optical excitation group, housed in said housing casing, comprising at least one light source delivering a wavelength in the excitation range of said molecular marker, designed to emit at least one excitation light radiation (λ, λ1) towards the sample when the sample is located in said at least one housing seat; - at least one detection group, designed to detect at least one emission light radiation (λ2), that can be generated, in use, from said at least one sample when the sample contains said at least one molecular marker and said at least one oligonucleotide probe, said at least one detection group being designed to supply at least one electric output signal (SOsignal output) correlated with the quantity, in said at least one sample, of said micro-RNA of interest; - at least one processing unit designed to receive and process said at least one electric signal and to output an index correlated with the quantity of said micro-RNA of interest in said at least one sample; said at least one container means being made of a material permeable to said at least one excitation light radiation (λ, λ1) and to said at least one emission light radiation (λ2) wherein said at least one group for detecting said emission light radiation (λ2) comprises at least one sensor means of silicon photomultiplier type; said at least one container means and said at least one detection group are integrated in a disposable cartridge insertable/disconnectable in/from said housing seat. - at least one device including a housing casing in which at least one housing seat is obtained for said at least one sample, and at least one opening through which said housing seat is accessible from the outside; - at least one container means for said at least one sample, said at least one container means being insertable/disconnectable in/from said housing seat through said at least one opening; - means for administering at least one molecular marker in said at least one container means, said at least one molecular marker being associable with said micro-RNA of interest in said sample; - at least one oligonucleotide probe, each oligonucleotide probe being set to establish a specific bond with a respective complementary sequence of nucleotides present in a strand of said micro-RNA of interest, said at least one oligonucleotide probe provided in said administration means or in said at least one container means; - at least one optical excitation group, housed in said housing casing, comprising at least one light source delivering a wavelength in the excitation range of said molecular marker, designed to emit at least one excitation light radiation (λ, λ1) towards the sample when the sample is located in said at least one housing seat; - at least one detection group, designed to detect at least one emission light radiation (λ2), that can be generated, in use, from said at least one sample when the sample contains said at least one molecular marker and said at least one oligonucleotide probe, said at least one detection group being designed to supply at least one electric output signal (SOsignal output) correlated with the quantity, in said at least one sample, of said micro-RNA of interest; - at least one processing unit designed to receive and process said at least one electric signal and to output an index correlated with the quantity of said micro-RNA of interest in said at least one sample; said at least one container means being made of a material permeable to said at least one excitation light radiation (λ, λ1) and to said at least one emission light radiation (λ2) wherein said at least one group for detecting said emission light radiation (λ2) comprises at least one sensor means of silicon photomultiplier type; said at least one container means and said at least one detection group are integrated in a disposable cartridge insertable/disconnectable in/from said housing seat.