South Africa’s National Health Laboratory Services (NHLS) Multi-morbidity Cohort.

South Africa’s National Health Laboratory Services (NHLS) Multimorbidity Cohort.

South Africa’s NHLS is the sole provider of laboratory services for the public sector health system, which serves 80% of the population across all provinces. Due to inconsistencies in reporting and recording of patient information associated  with laboratory tests, a single patient may be represented by several different sets of identifying information in the NHLS database. In collaboration with the NHLS, we previously linked the database using a graph-based probabilistic record linkage approach to create a validated, anonymous patient identifier and generate the ‘NHLS Multimorbidity Cohort’. Our algorithm, which was originally designed to identify unique individuals in the National HIV program, was expanded in 2019 (K01DK116929, PI Brennan) to include tests for HIV, tuberculosis, and noncommunicable chronic diseases (NCDs) (e.g., HbA1c, plasma glucose (fasting and random), serum creatinine (Scr), low density lipoprotein (LDL), triglycerides (TGs), total cholesterol (TC), high density lipoprotein (HDL)). Within the NHLS Multimorbidity Cohort, the algorithm demonstrated a positive predictive value (PPV) of 95.1% and a sensitivity of 78.3%. The high PPV indicates that the algorithm accurately identifies patient matches in 95% of cases. The NHLS Multimorbidity Cohort currently includes over 465 million laboratory measurements from 50 million unique patients, with 2.66 million aged 2–15 years, of whom 18.8% are YLWH and have at least one laboratory measurement between April 1, 2004, and March 31, 2017 (data up to December 2024 expected in early 2025). The database captures anonymized patient identifiers, biological sex, age, test dates, test types and results, and facility information but lacks additional clinical or demographic fields.