The measure can be scored via a diagnostic algorithm... or scored continuously from 0 to 27

The PHQ-9 and a patient-rated outcome measure (PROM) were administered to patients as part of the baseline assessment and at 2-, 4- and 6-week follow-up. The PHQ-9, the primary outcome in the trial, is a 9-item self-report instrument originally developed to screen for major depressive disorder in primary care settings. It can be scored continuously as a measure of symptom severity or with validated cut offs for mild (score = 5–9), moderate (score = 10–14), moderately severe (score = 15–19) and severe depression (score = 20–27)27,28 and has been validated in cancer populations.29,30 A threshold score of 10 can be used to identify a depression ‘case’. A single item PROM was also included in the trial, requesting the patient to indicate whether they felt ‘very depressed’, ‘quite depressed’, ‘a little depressed’ or ‘not depressed at all’.

http://journals.sagepub.com/doi/full/10.1177/026921631771132...

The measure can be scored continuously (from 0 to 27) or via a diagnostic algorithm that matches item responses to the diagnostic criteria of the DSM-IV (Kroenke, Spitzer, & Williams, 2001).

https://books.google.es/books?id=8nv_CQAAQBAJ&pg=PT166&lpg=P...

Depression
Depression was assessed at baseline and 12 weeks with the Patient Health Questionnaire-9 (PHQ-9).7 The PHQ-9 is a nine-item self-report instrument developed to screen for major depressive disorder in primary care settings by using Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria. It can be scored continuously for a measure of symptom levels and categorically for presumed diagnoses of major depression syndrome (MDS).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3341144/

It can be scored to provide a dichotomous diagnosis of probable major depression and to grade symptom severity via a continuous score.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3217785/

The PHQ-9 scored as a continuous measure with a cutoff score of ≥ 8 performed well in identifying MDD in cancer patients and should be considered as a screening instrument in this population.

Screening for Major Depression in Cancer Outpatients The Diagnostic Accuracy of... | Request PDF. Available from: https://www.researchgate.net/publication/45828736_Screening_... [accessed Jan 27 2018].

I've also seen 'summed-item score'

Scoring the instrument is completed by physicians using either a diagnostic algorithm or a

recommended cut-off score (Kroenke et al., 2001). Although the PHQ-9 can be scored using either method, the algorithm method has reported a low sensitivity and is not recommended. “A cut-off score of 10 or above on the summed-item score has been recommended as a method for screening for major depressive disorder” (Manea, Gilbody, & McMillan, 2015, p. 68).

https://scholarlyworks.lvhn.org/research-scholars-posters/41...