OBJECTIVES: Western Arabic numerals (i.e., 1, 2, 3) are the most frequently used number symbols, and almost exclusively appear in items or response options in patient-reported outcome assessments (PROs). Linguistic validation (LV) is the process of translating and culturally adapting PROs resulting in comprehensible, patient-friendly translations adapted for use in specific countries, cultures, or populations. Despite wide use and recognition of Western Arabic numerals, some languages have and preferentially use their own numeral systems. This research addresses a paucity of literature regarding such languages and the availability of detailed, PRO-centric information on their numeral systems, aiming to improve LV of numeric text.

METHODS: We surveyed 124 linguists representing 66 languages. Questions asked about the existence of unique numeral systems, contexts for use of Western Arabic and unique systems, preference for system use in daily life, and preference in writing vs typing.

RESULTS: 15/66 (22%) of languages in our sample reported some use of systems other than Western Arabic numerals. For languages using two systems, 8/15 (53%) noted important contextual factors dictating use, such as legal documents (e.g., Traditional Chinese), government documents (Thai), urban vs rural target demographics (Hindi), stylistic or specialized fields (Slovak; Catalan), or formality of intended language (Chinese – Simplified, Traditional). For both writing and typing in everyday use, 33% of linguists in multi-numeral system languages reported no system preference, while 20% preferred the unique system. All 66 languages reported familiarity with and use of Western Arabic numerals in daily contexts.

CONCLUSIONS: Results show Western Arabic numerals as the dominant numeral system, but reveal a non-trivial subset of languages with unique and contextually relevant numeral systems whose use should be considered in LV. For any PROs, and especially common types such as numeric rating scales, appropriate numeric localization to maximize patient comprehension is essential for collecting valid data.