Assessing Plasma C-Peptide Levels and Their Relationship with Health-Related Quality of Life in Patients with Prediabetes and Type 1 and Type 2 Diabetes

<b>Background/Objectives:</b> Understanding the relationship between plasma connecting peptide (C-peptide) levels and health-related quality of life (HRQoL) can inform diabetes management strategies. This study aimed to assess plasma C-peptide levels, HRQoL, and their association in patients with prediabetes, type 1 diabetes (T1D), and type 2 diabetes (T2D) attending outpatient departments (OPDs) in tertiary care hospitals. <b>Methods</b>: A cross-sectional survey was conducted between 1 January and 30 June 2023, using the EuroQoL Five Dimensions (EQ-5D-5L) instrument. Participants with prediabetes, T1D, or T2D were recruited from OPDs in diabetology, endocrinology, general practice, and family medicine at Sheikh Zayed Hospital (SZH) and Mayo Hospital (MH) in Pakistan. Plasma C-peptide levels were measured and HRQoL was assessed using EQ-5D-5L and the EQ Visual Analog Scale (VAS). <b>Results</b>: A total of 301 patients were included: 42 with prediabetes (14%), 70 with T1D (23.2%), and 189 with T2D (62.8%). The median C-peptide level was 0.46 nmol/L (IQR 0.13-0.85), the HRQoL score was 78.5% (IQR 63.2-100%), and the EQ VAS score was 85% (IQR 70-90%). C-peptide levels were significantly correlated with HRQoL scores (r = 0.14, <i>p</i> < 0.02) and differed across mobility, daily activity, pain/discomfort, and anxiety/depression domains (all <i>p</i> < 0.02). HRQoL scores significantly varied among the three groups (<i>p</i> < 0.0001), particularly in the aforementioned domains. <b>Conclusions</b>: C-peptide levels and HRQoL differ significantly across diabetes types, with lower C-peptide associated with reduced mobility, increased pain, and mental health issues. These findings underscore the importance of targeting C-peptide regulation to enhance HRQOL in diabetic populations.