Background <p>Although dipstick urinalysis has been widely used as part of health screening for employees, its efficacy in predicting renal function decline in healthy workers has not been elucidated.</p> Methods <p>We conducted a 10-year follow-up study of 33,139 Japanese healthy workers to determine the association between dipstick urinalysis results (urinary protein levels) and the development of adverse kidney outcomes (rapid eGFR decline and low eGFR) and to assess the predictive accuracy of dipstick urinalysis for the 10-year incidence of adverse kidney outcomes.</p> Results <p>Trace (±) and positive (1+, 2+, and 3+) dipstick proteinuria were found in 2.8% and 0.8% of the total, respectively. They had a significantly increased risk of adverse kidney outcomes than those who were negative. The sensitivity of dipstick urinalysis to discriminate between those with and without adverse kidney outcomes within 10 years was extremely low (0.01–0.07), while its specificity was nearly perfect (0.97–1.00). The sensitivity and specificity were robust to varying cutoffs (± or 1+) and to testing once or twice.</p> Conclusion <p>Workers who have at least one trace or positive result on dipstick urinalysis are more likely to have declining renal function within 10 years than those who do not. The specificity of almost 1.0 suggests that this noninvasive, inexpensive test will not miss workers whose renal function is expected to decline within the next 10 years. Occupational health staff should compile a list of workers with trace and positive results and ensure that those on the list take the necessary actions, such as retests and hospital visits, in a timely manner.</p>