The Diagnosis of Fungal Neglected Tropical Diseases (Fungal NTDs) and the Role of Investigation and Laboratory Tests: An Expert Consensus Report

Abstract

The diagnosis of fungal Neglected Tropical Diseases (NTD) is primarily based on initial visual recognition of a suspected case followed by confirmatory laboratory testing, which is often limited to specialized facilities. Although molecular and serodiagnostic tools have advanced, a substantial gap remains between the desirable and the practical in endemic settings. To explore this issue further, we conducted a survey of subject matter experts on the optimal diagnostic methods sufficient to initiate treatment in well-equipped versus basic healthcare settings, as well as optimal sampling methods, for three fungal NTDs: mycetoma, chromoblastomycosis, and sporotrichosis. A survey of 23 centres found consensus on the key role of semi-invasive sampling methods such as biopsy diagnosis as compared with swabs or impression smears, and on the importance of histopathology, direct microscopy, and culture for mycetoma and chromoblastomycosis confirmation in well-equipped laboratories. In basic healthcare settings, direct microscopy combined with clinical signs were reported to be the most useful diagnostic indicators to prompt referral for treatment. The survey identified that the diagnosis of sporotrichosis is the most problematic with poor sensitivity across the most widely available laboratory tests except fungal culture, highlighting the need to improve mycological diagnostic capacity and to develop innovative diagnostic solutions. Fungal microscopy and culture are now recognized as WHO essential diagnostic tests and better training in their application will help improve the situation. For mycetoma and sporotrichosis, in particular, advances in identifying specific marker antigens or genomic sequences may pave the way for new laboratory-based or point-of-care tests, although this is a formidable task given the large number of different organisms that can cause fungal NTDs.

<p>Emerging Invasive Fungal Infections: Clinical Features and Controversies in Diagnosis and Treatment Processes</p>

“…Automated ID consultations can improve fungal-related clinical issues but may not impact the time to appropriate antifungal therapy. 28 Medical experts unanimously agreed that microscopy and culture were the basic diagnostic tests for fungal infection at present, 31,32 and this study suggested that the consultations by superior physicians should be simple and timely so that patients can receive antifungal treatment as soon as possible to reduce hospital stays and medical expenses.…”

Estimation of the burden of tinea capitis among children in Africa

“…Cases were surprisingly mid‐aged adults with a mean age of 28 years. Yet, tinea capitis has largely been seen as a disease of poverty, mainly occurring in children from economically disadvantaged communities where overcrowding, sharing of fomites and poor hygiene are common 3,55 . High frequency of tinea capitis is observed in children between the age of 6–12 years, with male predominance 49 .…”

Histoplasmosis in the Republic of Congo dominated by African histoplasmosis, Histoplasma capsulatum var. duboisii

“…Also, the use of specific histochemical stains such as Giemsa, hematoxylin and eosin, Gomori methenamine silver, and periodic acid-Schiff facilitates the differentiation of these pathogens [46]. Detection of Hcc is also possible in approximately 40% of blood smears of patients with disseminated histoplasmosis [43][44][45], though this was not yet reported in the RoC. While antigen detection and PCR emerge as valuable adjunctive diagnostic tools, those are not yet available in the RoC.…”