Observation of functional activities might be carried at school and home as well.Though diagnosis in most of the world is done by an occupational therapist, in some countries diagnosis is made by certified professionals, such as psychologists, learning specialists, physiotherapists and/or speech and language therapists. Some countries recommend to have a full psychological and neurological evaluation if symptoms are too severe. Standardized tests
Sensory Integration and Praxis Test (SIPT)
Evaluation of Ayres Sensory Integration (EASI) – in development
DeGangi-Berk Test of Sensory Integration (TSI)
Test of Sensory Functions in Infants (TSFI)

Standardized questionnaires
Sensory Profile (SP)
Infant/Toddler Sensory Profile
Adolescent/Adult Sensory Profile
Sensory Profile School Companion
Indicators of Developmental Risk Signals (INDIPCD-R)
Sensory Processing Measure (SPM)
Sensory Processing Measure Preeschool (SPM-P)

Classification
Sensory integration and processing difficulties
Construct-related evidence relating to sensory integration and processing difficulties from Ayres early research emerged from factor analysis of the earliest test the SCISIT and Mulligans 1998 "Patterns of Sensory Integration Dysfunctions: A Confirmatory Factor Analysis". Sensory integration and processing patterns recognised in the research support a classification of difficulties related to:

Sensory registration and perception (discrimination)
Sensory reactivity (modulation)
Praxis (meaning "to do")
Postural, ocular and bilateral integration

Sensory processing disorder (SPD)
Proponents of a new nosology SPD have instead proposed three categories: sensory modulation disorder, sensory-based motor disorders and sensory discrimination disorders (as defined in the Diagnostic Classification of Mental Health and Developmental Disorders in Infancy and Early Childhood). 1. Sensory modulation disorder (SMD)
Sensory modulation refers to a complex central nervous system process by which neural messages that convey information about the intensity, frequency, duration, complexity, and novelty of sensory stimuli are adjusted.SMD consists of three subtypes:

Sensory over-responsivity.
The AAP has plans to review its policy, though those efforts are still in the early stages.A 2015 review of research on Sensory Integration Therapy (SIT) concluded that SIT is "ineffective and that its theoretical underpinnings and assessment practices are unvalidated", that SIT techniques exist "outside the bounds of established evidence-based practice", and that SIT is "quite possibly a misuse of limited resources".Some sources point that sensory issues are an important concern, but not a diagnosis in themselves.Critics have noted that what proponents claim are symptoms of SPD are both broad and, in some cases, represent very common, and not necessarily abnormal or atypical, childhood characteristics. Where these traits become grounds for a diagnosis is generally in combination with other more specific symptoms or when the child gets old enough to explain that the reasons behind their behavior are specifically sensory. Manuals
SPD is in Stanley Greenspans Diagnostic Manual for Infancy and Early Childhood and as Regulation Disorders of Sensory Processing part of The Zero to Threes Diagnostic Classification. Is not recognized as a stand-alone diagnosis in the manuals ICD-10 or in the recently updated DSM-5, but unusual reactivity to sensory input or unusual interest in sensory aspects is included as a possible but not necessary criterion for the diagnosis of autism. History
Sensory processing disorder as a specific form of atypical functioning was first described by occupational therapist Anna Jean Ayres (1920–1989).