There are innumerable questionnaires for dizziness, and the DHI is a popular one.
The dizziness handicap inventory was developed by the same authors who developed the tinnitus handicap inventory, (Jacobson et al, 1990).
The DHI is not a diagnostic test -- rather it produces scores related to the perceived dizziness handicap -- a subjective quantity.
The DHI is a 25 item test, and the maximum score is 100.
We also have a large repertoire of dizzy patients in our clinic practice , where we have obtained the DHI in a bit over 5000 of them. .
Unlike the situation with the THI (also developed by the same authors), this questionnaire looks as if it has some reasonable statistical properties. It looks somewhat like a normal curve, it is not very skewed like the THI. Now the scores above are not from normal control subjects - -these are people who are endorsing dizziness. They are claiming to be dizzy. So one cannot really say that it is "abnormal" to have such and such a score, but one can certainly say that among dizzy patients, most have a score of about 40, and it is very unusual to have a score of 100, but not so rare to have a score of 0.
Wong et asl (2022) used a score of 71 as their criteria for "extremely elevated" DHI. They found "The cut-off for eeDHI scores was 71. In total, 20.7% had eeDHI. Logistic regression identified 6 independent predictors for eeDHI scores: numbness in the face or body during dizziness (OR = 5.99, 95% CI 1.77-20.30), history of falls (OR = 4.37, 95% CI 1.74-10.97), female sex (OR = 2.81, 95% CI 1.18-6.66), caloric weakness (OR = 2.61, 95% CI 1.36-5.01), total number of diagnoses associated with dizziness (OR = 2.17, 95% CI 1.11-4.28), and total number of symptoms during dizziness (OR = 1.25, 95% CI 1.07-1.45)." They suggested that "These findings suggest that patients with eeDHI have severe disease and should be screened for falls."