The “Buruli Score”: Development of a Multivariable Prediction Model for Diagnosis of Mycobacterium ulcerans Infection in Individuals with Ulcerative Skin Lesions, Akonolinga, Cameroon

Le "Buruli Score" : Développement d'un modèle de prédiction multivariable pour le diagnostic de l'infection par Mycobacterium ulcerans chez les personnes présentant des lésions cutanées ulcéreuses, Akonolinga, Cameroun

Yolanda K Mueller (1) , Mathieu Bastard (1) , Patrick Nkemenang (2) , Eric Comte (2) , Geneviève Ehounou (2) , Sara Eyangoh (3) , Barbara Rusch (2) , Earnest Njih Tabah (4) , Laurence Toutous Trellu (5) , Jean-François Etard (1)

1 Epicentre [Paris] [Médecins Sans Frontières]
2 MSF - Médecins sans Frontières [Genève]
3 Centre Pasteur du Cameroun
4 National Leprosy, Yaws, Leishmaniasis and Buruli Ulcer Control Programme [Yaounde, Cameroon]
5 HUG - Hôpitaux Universitaires de Genève

Background: Access to laboratory diagnosis can be a challenge for individuals suspected of Buruli Ulcer (BU). Our objective was to develop a clinical score to assist clinicians working in resource-limited settings for BU diagnosis. Methododology/principal findings: Between 2011 and 2013, individuals presenting at Akonolinga District Hospital, Cameroon, were enrolled consecutively. Clinical data were collected prospectively. Based on a latent class model using laboratory test results (ZN, PCR, culture), patients were categorized into high, or low BU likelihood. Variables associated with a high BU likelihood in a multivariate logistic model were included in the Buruli score. Score cut-offs were chosen based on calculated predictive values. Of 325 patients with an ulcerative lesion, 51 (15.7%) had a high BU likelihood. The variables identified for the Buruli score were: characteristic smell (+3 points), yellow color (+2), female gender (+2), undermining (+1), green color (+1), lesion hyposensitivity (+1), pain at rest (-1), size >5cm (-1), locoregional adenopathy (-2), age above 20 up to 40 years (-3), or above 40 (-5). This score had AUC of 0.86 (95%CI 0.82-0.89), indicating good discrimination between infected and non-infected individuals. The cut-off to reasonably exclude BU was set at scores <0 (NPV 96.5%; 95%CI 93.0-98.6). The treatment threshold was set at a cut-off ≥4 (PPV 69.0%; 95%CI 49.2-84.7). Patients with intermediate BU probability needed to be tested by PCR. Conclusions/significance: We developed a decisional algorithm based on a clinical score assessing BU probability. The Buruli score still requires further validation before it can be recommended for wide use.

Mots clés: Cameroon; Diagnostic medicine; Polymerase chain reaction; Buruli ulcer; Lesions; Laboratory tests; Smell; Forecasting

Domaines: Maladies infectieuses; Dermatologie

Yolanda K Mueller, Mathieu Bastard, Patrick Nkemenang, Eric Comte, Geneviève Ehounou, et al.. The “Buruli Score”: Development of a Multivariable Prediction Model for Diagnosis of Mycobacterium ulcerans Infection in Individuals with Ulcerative Skin Lesions, Akonolinga, Cameroon. PLoS Neglected Tropical Diseases, 2016, 10 (4), pp.e0004593. ⟨10.1371/journal.pntd.0004593⟩. ⟨hal-02560725⟩