Table 4.

Associations between symptoms and positive urine dipstick results and kidney function and kidney injury

Symptoms and ResultsNumber of Events (N)Mean Difference (95% CI)Relative Means (95% CI)
eGFRNGALbNAGbIL-18bACR
CrudeAdjustedaCrudeAdjustedaCrudeAdjustedaCrudeAdjustedaCrudeAdjusteda
Symptoms, prior 3 moc,d
 Abdominal, back, flank pain63−3.1 (−8.3 to 2.1)−2.3 (−6.5 to 1.9)1.2 (0.9 to 1.7)1.2 (0.8 to 1.6)1.3 (0.9 to 1.7)1.2 (0.9 to 1.6)1.0 (0.7 to 1.3)0.9 (0.7 to 1.2)1.3 (0.9 to 1.8)1.3 (0.9 to 1.8)
 Burning or pain during urination283.0 (−1.6 to 7.6)3.7 (−2.1 to 9.4)1.5 (1 to 2.3)1.4 (0.9,2.1)1.1 (0.7 to 1.7)1.0 (0.7 to 1.6)1.3 (0.9 to 1.9)1.2 (0.8 to 1.8)1.0 (0.6 to 1.7)1.1 (0.7 to 1.8)
 Periods of frequent urination21−1.4 (−8.5 to 5.7)0.2 (−6.3 to 6.7)1.3 (0.8 to 2.1)1.1 (0.7 to 1.8)0.8 (0.5 to 1.3)0.7 (0.5 to 1.2)1.4 (0.9 to 2.2)1.3 (0.8 to 2)1.3 (0.7 to 2.3)1.3 (0.8 to 2.3)
 Any fever or chills28−2.1 (−8.3 to 4.1)1.2 (−4.8 to 7.1)1.5 (1 to 2.4)1.2 (0.8 to 1.9)1.8 (1.2 to 2.8)e1.5 (1 to 2.2)1.2 (0.8 to 1.8)1.0 (0.7 to 1.5)1.0 (0.6 to 1.6)1.0 (0.6 to 1.7)
Chistataf811.7 (−2.6 to 5.9)1.4 (−2.5 to 5.4)1.4 (1 to 1.8)e1.3 (1 to 1.7)1.2 (0.9 to 1.6)1.1 (0.9 to 1.5)1.2 (0.9 to 1.5)1.1 (0.9 to 1.5)0.8 (0.6 to 1.2)0.9 (0.6 to 1.2)
Health-related behaviors and diagnoses, prior 3 moc,d
 Taken antibiotics31−0.4 (−6.4 to 5.6)−1.3 (−6.8 to 4.1)1.1 (0.7 to 1.7)1.2 (0.8 to 1.9)1.3 (0.9 to 2)1.5 (1 to 2.2)e1.1 (0.8 to 1.6)1.2 (0.8 to 1.7)1.1 (0.7 to 1.8)1.2 (0.7 to 1.8)
 Taken pain medications >3 d34−5.3 (−12.4 to 1.8)−2.8 (−8.2 to 2.5)1.4 (0.9 to 2)1.3 (0.9 to 1.9)1.5 (1 to 2.3)e1.4 (1 to 2.1)1.5 (1.1 to 2.2)e1.4 (1 to 2)0.7 (0.5 to 1.2)0.7 (0.5 to 1.1)
Dipstick parameters, preharvestg
 Leukocyte esterase11−2.7 (−12.2 to 6.9)−1.8 (−10.6 to 7.0)1.6 (0.8 to 3.3)1.5 (0.8 to 2.9)1.5 (0.8 to 2.9)1.3 (0.7 to 2.5)1.3 (0.7 to 2.5)1.3 (0.7 to 2.3)1.0 (0.5 to 2.2)1.1 (0.5 to 2.3)
 Proteinuria6−0.9 (−13.7 to 11.9)2.8 (−8.9 to 14.5)6.7 (2.7 to 16.2)e4.9 (2.1 to 11.6)e3.8 (1.6 to 9.1)e3.0 (1.3 to 6.7)e3.0 (1.3 to 6.6)e3.1 (1.4 to 6.9)e5.7 (2.1 to 15.7)e5.5 (2.1 to 14.4)e
Dipstick parameters, late harvestg,h
 Leukocyte esterase29−13.3 (−25.0 to −1.6)e−12.9 (−18.7 to −7.0)e3.4 (2.2 to 5.1)e2.8 (1.8 to 4.3)e1.5 (1 to 2.2)1.0 (0.7 to 1.6)0.6 (0.4 to 0.9)e0.5 (0.3 to 0.7)e1.0 (0.6 to 1.6)0.9 (0.6 to 1.5)
 Proteinuria8−14.1 (−37.5 to 9.3)−10.9 (−21.1 to −0.7)e3.7 (1.7 to 8.1)e3.0 (1.4 to 6.6)e2.5 (1.2 to 5.5)e2.1 (1 to 4.3)2.5 (1.3 to 5.1)e3.1 (1.5 to 6.3)e12.4 (5.3 to 28.9)e9.4 (4.2 to 21.4)e
 Blood21−10.6 (−23.0 to 1.9)−8.5 (−15.0 to −2.0)e0.9 (0.5 to 1.4)0.8 (0.5 to 1.3)1.6 (1 to 2.7)e1.5 (0.9 to 2.3)1.0 (0.6 to 1.5)1.0 (0.7 to 1.6)1.7 (1 to 3)1.6 (0.9 to 2.7)
  • NGAL, neutrophil gelatinase-associated lipocalin; NAG, N-acetyl-β-d-glucosaminidase; ACR, albumin-creatinine ratio.

  • a Adjusted for age, employment duration, and job category.

  • b All crude and adjusted models predicting NGAL, NAG, and IL-18 were additionally adjusted for urinary creatinine.

  • c Reference was workers not reporting symptoms or health-related behaviors.

  • d Workers reported symptoms and health-related behaviors during late-harvest data collection.

  • e P<0.05.

  • f Chistata is a colloquial term that describes a set of symptoms including painful urination, burning during urination, and back pain.

  • g Reference was workers with negative dipstick results.

  • h Cross-sectional analyses.