On the other hand, the main features of perfectionism and inflexibility can result in considerable suffering in an individual with OCPD as a result of the associated need for control.The presence of OCPD in patients with OCD has been linked to a worse prognosis of OCD, especially when cognitive behavioral therapy was used. This may be due to the ego-syntonic nature of OCPD which may lead to the obsessions becoming aligned with ones personal values. In contrast, the trait of perfectionism may improve the outcome of treatment as patients are likely to complete homework assigned to them with determination. The findings with regards to pharmacological treatment has also been mixed, with some studies showing a lower reception to SRIs in OCD patients with comorbid OCPD, with others showing no relationship.Comorbidity between OCD and OCPD has been linked to a more severe presentation of symptoms, a younger age of onset, more significant impairment in functioning, poorer insight, and higher comorbidity of depression and anxiety. Autism spectrum disorder
There are considerable similarities and overlap between autism spectrum disorder (ASD) and OCPD, such as list-making, inflexible adherence to rules, and obsessive aspects of ASD, although the latter may be distinguished from OCPD especially regarding affective behaviors, worse social skills, difficulties with Theory of Mind and intense intellectual interests, e.g. an ability to recall every aspect of a hobby. A 2009 study involving adult autistic people found that 32% of those diagnosed with ASD met the diagnostic requirements for a comorbid OCPD diagnosis.
A diagnosis of OCPD is only received when four out of the eight criteria are met.The eight criteria of OCPD described in the DSM-5 (of which four are required to be present in a patient for a diagnosis) are:

Preoccupation with details
Perfectionism interfering with task completion
Rigidity and stubbornness
Reluctance to delegate
Excessive conscientiousness and pedantry (excessive concern with minor details and rules)
Workaholic behavior
Miserliness (excessive desire to save money)
Unable to discard worn-out or worthless objectsThe list of criteria for the ICD-10 is similar, but does not include the last three criteria in the above list, and additionally includes the symptoms "intrusive thoughts" and "excessive doubt and caution" as criteria for diagnosis. Alternative model for diagnosis
The DSM-5 also includes an alternative set of diagnostic criteria as per the dimensional model of conceptualizing personality disorders. Under the proposed set of criteria, a person only receives a diagnosis when there is an impairment in two out of four areas of ones personality functioning, and when there are three out of four pathological traits, one of which must be rigid perfectionism. The patient must also meet the general criteria C through G for a personality disorder, which state that the traits and symptoms being displayed by the patient must be stable and unchanging over time with an onset of at least adolescence or early adulthood, visible in a variety of situations, not caused by another mental disorder, not caused by a substance or medical condition, and abnormal in comparison to a persons developmental stage and culture/religion.