Clinical Practice Guideline

for

IgA NEPHROPATHY

Developed for the

Aerospace Medical Association

by their constituent organization

American Society of Aerospace Medicine Specialists

 

Overview: IgA nephropathy is the most common cause of glomerulonephritis, responsible for approximately 45% of cases.  A peak incidence in the second and third decades of life exists, but patients may present at any age.  It occurs primarily in Asians and Caucasians, rarely in blacks.  IgA nephropathy predominantly occurs in males (2:1) in North American and Western European populations.  Originally thought to be benign, it is now known that many cases can progress to renal failure.  For the purpose of this discussion, it is assumed the workup for hematuria and/or proteinuria has been completed, and there is a final diagnosis of biopsy-confirmed IgA nephropathy.  The issue of biopsy may present a problem, since many nephrologists in the United States will not recommend a biopsy unless proteinuria exceeds 500 mg/day. 

 

Aeromedical Concerns: Flyers with IgA nephropathy may have disease ranging from totally benign to rapidly progressive renal failure.  The risk of sudden incapacitation is negligible.  Clinical predictors of progressive disease: 24-hour urine protein greater than 500 mg, serum creatinine 2.5 or more, and hypertension.  Studies have been conducted looking for other markers of progression: the serum IgA/C3 ratio, histologic features such as crescent formation and interstitial fibrosis, and isolated microscopic hematuria, but these are recent and there’s not enough data to make them clinically useful. 

 

Aeromedical Disposition (Military): Air Force: AFI 48-123 V3 A4.22.3 places the limit at 200 mg per 24 hours.  Waivers are considered for fixed or reproducible orthostatic (postural) proteinuria, and have been granted for IgA nephropathy if the clinical predictors of disease are acceptable.

Army: Same as above.

Navy:  Similar to the AF.  The Navy waiver guide does not define “normal renal function.”

 

Medical Workup:

 

  • 2 or more urine dipsticks positive for protein
  • Microscopic examination of urine
  • Serum BUN and creatinine
  • Urine SSA
  • At least one 24-hour urine protein
  • Split urine test (see protocol)
  • Total protein-to-creatinine ratio (Pr/Cr) on first morning urine specimen, AND second sample taken after patient is upright
  • Patients with persistent proteinuria, not explained by postural change, need referral to a nephrologist.

 

The urine protein/creatinine ratio (Pr/Cr) is commonly used in lieu of the 24-hour protein.  However, it does have its limitations, which may be germane to aeromedical concerns.  Pr/Cr accuracy relies on the assumption that daily creatinine excretion is 1000 mg (8.8 mmol)/day; it increases in muscular people, and decreases with cachetic patients.  An increased creatinine excretion will underestimate proteinuria, and may be an issue in a young, muscular pilot population.  Collecting this data in a younger population may yield better guidelines for its use at a later time.

 

Waiver Experience (Military): Waivers have been granted for IgA nephropathy if the proteinuria is below 1000 mg in 24 hours (12 of 14 cases in AIMWTS ).  Review of the electronic records shows both the disqualified cases had one or more of the clinical predictors for advancing disease.

 

Waiver Experience (Civilian): Since there is little risk of incapacitation from IgA nephropathy itself, conditions secondary to chronic kidney failure will be important, especially blood pressure.

 

References:

 

1.     Cattran D C. Treatment and prognosis of IgA nephropathy UpToDate 2007 Retrieved September 27, 2007 from the World Wide Web: http://uptodateonline.com/online/content/topic.do?topicKey=glom_dis/10588

 

2.     Barratt J. Causes and diagnosis of IgA nephropathy UpToDate 2007 Retrieved September 27, 2007 from the World Wide Web: http://uptodateonline.com/online/content/topic.do?topicKey=glom_dis/8139

 

3.     Boulware L E. Screening for proteinuria in US adults. JAMA 2003: 3101-3114

 

4.     US Air Force Instruction 48-123. Medical examinations and standards. Washington, DC: U.S. Air Force; 5 June 2006

 

5.     US Army Regulation 40-501. Standards of medical fitness. Washington, DC: Headquarters, Department of the Army; 1 February 2005

 

6.     US Federal Aviation Administration. Guide for Aviation Medical Examiners.  Washington, DC, US Dept. of Transportation, Federal Aviation Administration, April 3 2006.

 

7.     US Navy.  Aeromedical Reference and Waiver Guide. 13 march 2007 Retrieved December 15, 2007 from the World Wide Web: http://www.nomi.med.navy.mil/NAMI/WaiverGuideTopics/index.htm

 

 

July 22, 2008