Nitrite Dipstick Urinalysis as a Point-Of-Care Test for Sodium Nitrite Poisoning

BACKGROUND: Intentional sodium nitrite poisoning is an emerging trend worldwide, as it is promoted for its use in self-euthanasia. Nitrite dipstick urinalysis could potentially serve as a rapid-diagnostic tool. Urine dipstick analysis is a common point-of-care test (POCT) for the initial diagnosis of urinary tract infections. The aim of this study was to investigate nitrite dipstick urinalysis as a potential reliable POCT for the early detection of sodium nitrate poisoning.

METHODS: Postmortem urine samples, collected over 1 year, were prospectively analyzed for nitrite presence using a urine dipstick method. In addition, a retrospective search was conducted in the database to identify cases with suspected or confirmed sodium nitrite poisoning as the cause of death. Available urine samples from these cases were screened for the presence of nitrite.

RESULTS: Prospectively, 10 of the 420 urine samples tested positive for nitrite presence: 6 samples without any suspicion of sodium nitrite ingestion and 4 with confirmed sodium nitrite poisoning as the cause of death. In addition, in our retrospective study, 12 cases of suspected sodium nitrite poisoning were tested for nitrite presence in the urine using the dipstick. Of these, 8 tested positive for nitrite. Two of the 12 cases were later attributed to intoxication with other substances. As a control, urine samples spiked with sodium nitrite were tested using the dipstick; the pink color intensified with increasing sodium nitrite concentration.

CONCLUSIONS: Nitrite dipstick urinalysis is a feasible approach for the early detection of nitrite poisoning in postmortem toxicological screening. In addition, this rapid POCT shows potential as a diagnostic tool for use in acute clinical settings in cases of suspected sodium nitrite poisoning or elevated methemoglobinemia with an unknown cause.