Autism spectrum disorders (ASDs) affect 1-2% of children [¹–⁵]. Early detection is important because it allows the introduction of early intensive treatment strategies to improve the psychosocial adjustment of these children [⁶–¹³]. The development of measurements to assess the autism spectrum disorders in the last two decades has increased. Unfortunately, the cost of using these tools for clinical and research purposes has become expensive and complicated [¹⁴]. Many of these instruments are very complex and targeted to specialized professionals with experience in autism, so their use in the primary care setting in Mexico is not feasible. Furthermore, some of them require training and take enormous time to administer and score [¹⁵, ¹⁶]. Education level and skills and attributes of parents, in addition to health and educational services, have a crucial role in recognition and diagnosis of ASD. First concerns are noticed by parents at 12–24 months of age [¹⁷, ¹⁸]. These initial observations of atypical development are followed by two types of delays to seek actions. Parental delays in seeking attention are approximately 4 months, and medical delay in assigning a diagnosis (from first reported concern to medical diagnosis) is 30.1 months [¹⁹]. In Latin-American countries most parents seek initial attention through public health services [²⁰], but only 38% receive their diagnosis through this means [¹⁹]. Furthermore, recent studies show that many children are identified in school [²¹] so screening instruments need to be oriented to parents, teachers, and primary medical health providers.

The Modified CHAT (M-CHAT) (Robins et al., 2001) [⁵] is a simple questionnaire for parents that can be completed in 10 minutes. According to the authors, this instrument improves discrimination between autism and other developmental problems. The M-CHAT reported sensitivity and specificity  .87, and  .99, respectively, positive predictive power of  .80 and negative predictive power  .99. [⁵] The sensitivity and specificity of the M-CHAT was determined by using 2 criteria: (1) failing 2 critical items (critical) or more of the 6 critical and (2) failing 3 or more critical items (if any) of the 23 total. According to the authors [⁵] the sensitivity and specificity for criterion 1 was  .97 and  .95, and criterion 2 was  .95 and  .99, respectively. Internal consistency was adequate for the full list of symptoms (α = .85) and for the 6 critical items (α = .83).

Mexico needs reliable and valid screening instruments for autism for use in the primary level of health care and education services. The purpose of this study was to investigate the psychometric properties of the Mexican (MM-CHAT-version) in a sample of referred young children with presumptive diagnosis of ASD and a sample from the general population.

This study investigated the psychometric properties of the MM-CHAT Spanish version for Mexico in two different samples: clinical and TD from the general community. Most validation studies of the M-CHAT [²⁵, ²⁶] including the original [⁵] have used large samples of the general population to identify a very small number of children with autism (n = 4 and n = 7, resp.). In this study we used a case control design which included a large clinical group of children who were seen in the outpatient PDD clinic before an autism diagnosis was assigned. Overall the MM-CHAT could discriminate between the TD and the ASD group. The instrument showed moderate internal consistency and convergent validity with CBCL/1.5–5. However, there are some results which deserve a more detailed analysis. ADI-R Spearman correlations with MM-CHAT scores were varied (rho = .23–.66), this result is consistent with the notion that autism is a complex and heterogeneous disorder. However, overall MM-CHAT-T correlations were better than the MM-CHAT6ci particularly for the ADI-R (BV) and C dimensions (rho  .23, P < .07 and rho  .36, P < .01), this gain represents a small drop in the A dimension correlation from  .66 to  .61 with the same P < .01 value. An addition of items exploring communication abnormalities such as echolalia, language loss and/or delay salient aspects of autism could make the BV correlation rise and become significant.

All kappas were significant using the MM-CHAT-2 criteria (best cutoff in this study) and the ADI-R cutoff domains except for the dimension C(κ).17 P = .09.   The MM-CHAT-T had a higher concordance with the ADI-R nonverbal dimension (BNV) (κ)  .61 P = .0001 in contrast to the B verbal (BV) dimension and the C dimension of stereotypical behavior (κ).29 P = .004, and (κ) .16 P = .01. This result supports the idea suggested by other researchers that the M-CHAT detects better nonverbal children with low functioning autism [²⁷, ²⁸].

The MM-CHAT showed discriminant validity between the ASD and the TD group through analyzing differences on the MM-CHAT-T means and percentage of failed items. Critical items in this study are not the same as the one proposed in the original study.

The detection of the Critical items has been inconsistent in the studies [⁵, ²⁶]. Some factors such as the sample composition (clinical versus community) or age range and the statistical procedures to derive them could explain these differences. Nevertheless, there is growing evidence from studies with combined samples from different race composition which suggests a cultural bias does exist for autistic measures like M-CHAT [²⁹] and other standardized measures for autism [³⁰].

However, as more international studies of validation are published it is becoming evident that the M-CHAT has important differences in items that parents endorsed more frequently. The reason for this cultural bias is unclear, but it is possible that differences in parenting and social behavior styles could be influencing this phenomenon. Many rating scales for autism are dichotomic because they were developed when autism was understood as a categorical disorder. Recent evidence suggests that autism traits are normally distributed in the general population [³⁰–³⁶] and that not only parents, but also individuals without autism in their families express these traits. Based on this latter evidence, the suggestion made by some researchers [²⁶, ³⁷] to modify the M-CHAT as a quantitative measure with items reorganized as a likert scale type seems appropriate. In 2007, a supplementary telephone interview for parents of children who screened positive was developed [³⁸]. The combined use of the M-CHAT screen and the telephone interview increases its positive predictive value without adversely affecting its sensitivity [³⁸]. However, this incremental validity will raise the cost of M-CHAT excessively for countries like Mexico. There are important reasons to screen and take action at the same time. The addition of an interview requires training which can be very difficult to give and maintain in busy settings.

As in other studies, we also observed that some parents do not understand all of the MM-CHAT questions [²⁵]. This has been attributed to a low education level of the caregiver. There is incipient evidence that contradicts this idea [³⁹]. Autism signs are bizarre, elusive and some of them transient, so even highly educated parents can miss these symptoms. Parents might believe it to be irrelevant if their children do not point to share pleasure. Furthermore, parents of children with autism often share some autistic traits and there is evidence of assortative mating for these traits among spouses [⁴⁰, ⁴¹]. It is unknown if having these traits can weaken the parents' abilities to detect them in their children. In some Asian and Latin-American cultures like Mexico, making eye contact is considered inappropriate and a sign of disrespect. Some mothers discourage children from pointing with the index finger because it is considered to be rude [⁴², ⁴³].

These cultural issues could explain some of the inconsistency in items responses independent of the instrument [⁴⁴]. For these reasons, developmental assessment is one of the most challenging tasks for service providers and parents. The addition of pictograms employed by Inada et al., 2011 [²⁶] is a proposal that deserves more investigation. Up to date no prevalence studies on autism have been done in Mexico. In this study, 5% of parents in the TD group met the MM-CHAT-2 criteria. This figure gives support to the urgent need to develop and/or validate gold standard instruments to confirm an autism diagnosis.

This study has some limitations. Despite having a large sample of undiagnosed ASD children from the psychiatric outpatient PDD clinic, we were unable to include the IQ tests results and analyze the effect of this variable on the MM-CHAT cutoff performance. The majority of young children were unmedicated, but others with challenging behaviors had medication for their hyperactivity and irritability, which could bias some of the parents' responses. Overall, in this study we demonstrated that the MM-CHAT can discriminate between ASD and TD children. The instrument has good psychometric properties and can be used for screening purposes in primary settings or busy specialized psychiatric clinics. However, these results support evidence for cultural differences in item responses, making it difficult to compare M-CHAT results internationally.