Syndrome of Inappropriate ADH Secretion: Sensitivity and Specificity

Introduction: SIADH a major cause of hyponatremia and represents the condition when a euvolemic patient has increased ADH causing inappropriate retention of free water. The diagnosis is important as the treatment is fluid restriction rather than normal saline infusion.

For a review of the diagnosis, see http://cjasn.asnjournals.org/cgi/content/full/3/4/1175 (PMID 18434618)

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Differential Diagnoses include: Hypovolemia

Prevalence

The sensitivity and specificity of findings for Syndrome of Inappropriate ADH Secretion are listed below. See the left navigation bar to change the display.

Hypovolemia

Finding	Sensitivity	Specificity	Comments, Study
Fractional Excretion of Sodium	68%	100%	FENa > 0.5% Study: Clin J Am Soc Nephrol. 2008 Jul;3(4):1175-84. PMID: 18434618
Fractional Excretion of Urea	52%	80%	FEUrea > 50% Study: Clin J Am Soc Nephrol. 2008 Jul;3(4):1175-84. PMID: 18434618
Plasma Urea	80%	80%	plasma Urea < 30 mg/dl suggests SIADH (because of dilution) Study: Clin J Am Soc Nephrol. 2008 Jul;3(4):1175-84. PMID: 18434618
Uric Acid	73%	59%	uric acid < 4mg/dl suggests SIADH (because of dilution) Study: Int Urol Nephrol. 2001;32(3):475-93. PMID: 11583374
Urine Sodium	90%	70%	UNa > 30 indicates SIADH. However, UNa can be high in hypovolemic patients, especially those with low UOP. Study: Clin J Am Soc Nephrol. 2008 Jul;3(4):1175-84. PMID: 18434618

Untagged

Finding	Sensitivity	Specificity	Comments, Study
Clinical Assessment of Volume Status	48%	53%	Study: Am J Med. 1987 Nov;83(5):905-8. PMID: 3674097