Prevalence and comorbidities of autism among children referred to the outpatient clinics for neurodevelopmental disorders

Introduction Autism spectrum disorders (ASD) is a neurodevelopmental disorder that has been rarely diagnosed in Sub-Saharan Africa. Although a proportion of children do present features of ASD in the Democratic Republic of Congo (DRC), little is known about it prevalence. Often, the co-morbidities constitute the upfront symptoms and therefore may it recognition and management difficult, aggravating as such the prognosis. The present study therefore aimed at studying the clinical profile of autism spectrum disorder (ASD) and the associated morbidities among children and adolescents in outpatient clinics in Kinshasa, the Democratic Republic of Congo. Methods We conducted a cross sectional study in the three outpatients centers receiving patients referred for neurodevelopmental disorders in Kinshasa, DRC, from June 2008 to June 2010. A total of 450 subjects aged from 1-18 years old were referred and included in the study. The clinical diagnosis for ASD was made using the DSM-IV-R and the ADIR. Co-morbidities were identified using DSM-IV-R criteria together with an extensive clinical interview and observation. All patients were subject to an intellectual quotient evaluation and an electroencephalogram reporting. Results Of the 450 subjects referred, 120 (29.3%) received the diagnosis of ASD, with boys outnumbering girls (OR 3:1. The mean age was 7.9 years (SD 3.4) (p< 0.001). Intellectual disability (75.83 %) and epilepsy (72.50%) were the main co-morbidities significantly associated with autism (p< 0.001). It was also found that co-morbidities were most frequent in subjects with an IQ<70 (p=0.05). Conclusion ASD is frequent among patients referred for neurodevelopmental disorders in the three outpatients’ centers for neurodevelopmental disorders in Kinshasa. Males seem to be more affected than female. The main co-morbidities were epilepsy and intellectual disabilities. Our findings suggest that it is important to screen for ASD and co-morbidities among all subjects referred for neurodevelopmental disorders and to undertake survey on ASD in various structures of rejected children from the society in Kinshasa DRC. This will help to identify and manage ASD and associated co-morbidities at an early stage for a better prognosis.

Intellectual disability, epilepsy and ADHD can share a common neurobiological basis [3,13] and are factors of poor prognosis of autism [3,14]. Comorbidities are the main reasons for referral to outpatient clinics and admission to hospitals. They mask and delay the diagnosis and are the cause of inadequate therapies [6,15,16] .That is why Gadow, Devincent, & Schneider, 2008 [17] strongly recommend looking at the presence of comorbidities before starting any treatment of autism.
There are little data on the prevalence of autism in Sub-Saharan Africa [18]. Autism is rarely diagnosed in these countries because it is confused with development, neurological or psychiatric disorders, with dumbness and with deafness [6,19]. In addition, autism is treated independently from its comorbidities in specialized neurodevelopmental disorder treatment centers and in general medical settings [19]. Consequently its magnitude is hidden which does not help for planned cares of children suffering from autism. In the study on diagnosis and interventions in children with autism, intellectual disability, deafness and other handicaps, Mukau [ [19]. Autism Diagnosis Interview Revised (ADIR) [21]; was used to diagnose autism. Children without autism on ADIR (n=56) and those whose parents or tutors were not present during interviews (n=20) or refused ADIR interview (n=7) and those who were under 3 years at the end of the study (n=10) were excluded.

Procedures and techniques of data collection
We looked at socio-demographic characteristics and co-morbidities in children diagnosed with autism. The diagnosis of comorbidities was done by medical history carried out with children's parents, clinic neuropsychiatric observation, DSM-IV-R criteria [1], audiometric, assessment of Intellectual Quotient of performance (IQ) and electroencephalography (EEG). The audiometric assessment was done by the ENT-specialist in order to exclude hearing impairments, which is often misdiagnosed in children with ASD and because children with autism seem to be deaf without being like it and deafness may be a comorbidity of autism.

Assessment of intellectual level through the Wechsler Performance
Test (WISC-R) [22] was done by the clinical psychologist.

Profile of disorders in children referred to outpatient clinics for neurodevelopmental disorders
In a comparative view of autism with other development disorders, Table 1 Table 2).

Autism and co-morbidities
Cognitive disorders or intellectual disability according to Performance IQ (75.83 %) and epilepsy (72.50%) were the main comorbidities significantly associated with autism (p<.001) ( Table   3). In total, 93.33% of cases had 1 to 4 comobidities and the EEG showed abnormal activities even in cases without comorbidities (Table 4). Table 4 also shows that 6.67% (

Discussion
This study aims at determining the prevalence and co morbidities of Autism among children referred to the outpatient clinic of Neurodevelopmental disorders. There was male predominance in autism which is consistent with data reported in Western countries [4] as well as in Africa [8,18,19].  [11,27,28]. The significant relationships between autism, intellectual disability, and epilepsy which are the three main neurodevelopmental disorders in our study prove the damaging role of early cerebral morbidity. The harmful role of these factors is known to be involved in the pathogenesis of neurodevelopment disorders [13,29,30] .In addition, intellectual disability and epilepsy are known to be predictor factors of worse prognosis, morbidity and mortality of autism [14].
Our study showed on the one hand, the increase of frequency of intellectual disability and the decrease of IQ with co morbidities, and one the other hand the high frequency of pathological EEG even in the case of autism without co morbidities. Mukau [19] and Rommelse et al. [3] assumes that some co morbidities can be responsible for weak IQ but Pry R et al. [31] think that the sociocognitive factors can affect the IQ and improve it in the growing age. We think that EEG perturbations in autism without co morbidities are an argument for the neurobiological bases of this disease [3,6,7]. These data suggest the need of conducting a genetic study on autism co morbidity in our area. The findings of this study will enable to make a difference between genetic and environmental factors in order to direct the genetic counsels and minimize the impact of culture on the origin of autism [18]. The proportion of pathological audiometric test (25.83 %) was high compared to the data reported in the literature (5.9 to 17%) [32,33]. This high proportion may be due to the early cerebral morbidity in African areas.
ADHD is frequently associated with autism. The diagnosis of this disorder is difficult to make when it is associated with autism. The

Competing interests
The authors declare no competing interest.