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Table 1 Current parasitological techniques, related challenges and research needs for a potential application of MALDI-TOF MS as diagnostic tool for major helminths of human and veterinary importance

From: MALDI-TOF mass spectrometry as a diagnostic tool in human and veterinary helminthology: a systematic review

Characteristics Nematodes Cestodes Trematodes
Helminth species Soil-transmitted helminths: Ascaris lumbricoides; hookworm; Strongyloides stercoralis; Trichuris trichiura Tissue nematodes: Dirofilaria spp.; Trichinella spp.; Toxocara spp.; Wuchereria bancrofti and other agents causing lymphatic filariasis, Onchocerca volvulus, Loa loa; animal hookworms causing cutaneous larva migrans Taenia spp.; Diphyllobothrium latum Echinococcus spp. Schistosoma spp.; Fasciola hepatica; small liver flukes
Type of diagnostic sample (i) Stool; (ii) Excreted worms (i) Tissue samples; (ii) Serum; (iii) Extracted worms (e.g. Loa loa) (i) Stool; (ii) Serum (for T. solium); (iii) Tissue samples in cysticercosis; (iv) Excreted proglottids (i) Stool (in animals); (ii) Tissue biopsies, surgical samples; (iii) Serology (i) Stool; (ii) Urine; (iii) Serum; (iv) Tissue biopsies
Parasitological standard diagnostic techniques (i) Stool microscopy (e.g. Kato-Katz technique); (ii) PCR in reference laboratories (i) Direct identification on biopsy samples; (ii) Serology; (iii) PCR in reference laboratories; (iv) Detection of microfilariae in blood; (v) Detection of antigen in blood (Wuchereria) (i) Direct identification of faecally excreted proglottids; (ii) Stool microscopy; (iii) Serology (i) Microscopy; (ii) PCR of cysts and tissue samples; (iii) Serology (i) Stool/urine microscopy (dependent on infecting species); (ii) Rapid diagnostic test for circulating cathodic antigen (CCA) in urine; (iii) PCR on serum, stool or urine; (iv) Serology
Difficulties related to currently employed diagnostics (i) Low sensitivity in light infection intensities; (ii) Specific concentration techniques needed for S. stercoralis; (iii) Misidentification of hookworm and S. stercoralis larvae possible; (iv) No species differentiation between different hookworm species possible upon microscopy (i) Serology frequently false-negative; (ii) False-negative PCR results in case of ‘new’ species; (iii) Lack of expertise outside specialized laboratories (i) Eggs of related Taenia spp. are indistinguishable by microscopy; (ii) Lack of expertise in proglottid differentiation in many laboratories (i) Serology frequently false-negative in intact cysts; (ii) Microscopy (similar morphology) and serology (cross-reactivity) cannot reliably distinguish between Echinococcus spp. (therapeutic implications) (i) Low sensitivity in light infection intensities; (ii) Microscopy and PCR fail to detect hybrid species
Research needs for MALDI-TOF application (i) Establishment of a database for identification of eggs/larvae and adult worms; (ii) Differentiation of microscopically indistinguishable hookworm species; (iii) Protocol development for application on stool samples and bronchial specimens (i) Establishment of a database for identification of tissue-invasive helminths; (ii) Species differentiation within one genus (e.g. Dirofilaria); (iii) Application on biopsy specimens; (iv) Detection of microfilariae in blood; (v) Detection of antigen in blood (e.g. Wuchereria spp.) (i) Establishment of a database for identification of Taenia proglottids and eggs; (ii) Differentiation between T. solium eggs/proglottids and other Taenia spp.; (iii) Protocol development for application on stool specimens (i) Establishment of a database for species-specific identification of eggs and tissue cysts; (ii) Protocol for application on different sample types (i) Establishment of a database for species-specific identification; (ii) Protocol for application on different sample types; (iii) Detection of Schistosoma antigen(s) in serum; (iv) Detection of products derived from helminth-specific metabolism in serum samples