SUSPUP and SUSPPUP

SUSPUP and SUSPPUP
Synonyms	(serum sodium to urinary sodium to serum potassium to urinary potassium) and (serum sodium to urinary sodium to serum potassium^2 to urinary potassium)
Reference range	3.6–22.6 (SUSPUP) 0.6–5.3 (SUSPPUP)
Test of	Extent of hormonal stimulation of sodium absorption and potassium excretion in kidney's tubules and collecting tubes

SUSPUP (serum sodium to urinary sodium to serum potassium to urinary potassium) and SUSPPUP (serum sodium to urinary sodium to (serum potassium)^2 to urinary potassium) are calculated structure parameters of the renin–angiotensin-aldosterone system (RAAS). They have been developed to support screening for primary or secondary aldosteronism.[1][2]

Physiological principle

The steroid hormone aldosterone stimulates the reabsorption of sodium and the excretion of potassium in the distal tubuli and the collecting tubes of the kidneys. Calculating SUSPUP and/or SUSPPUP helps to determine the intensity of mineralocorticoid signalling, which may be helpful in the differential diagnosis of hypertension and hypokalaemia.^[citation needed]

Preconditions of testing

Sodium and potassium concentrations have to be determined in serum and spot urine probes that have been obtained simultaneously or within a short time interval between.^[citation needed]

Calculation

${\displaystyle SUSPUP={\frac {\frac {{[Na}^{+}]_{Serum}}{{[Na}^{+}]_{Urine}}}{\frac {{[K}^{+}]_{Serum}}{{[Na}^{+}]_{Urine}}}}}$

${\displaystyle SUSPPUP={\frac {\frac {{[Na}^{+}]_{Serum}}{{[Na}^{+}]_{Urine}}}{\frac {{[K}^{+}]_{Serum}^{2}}{{[Na}^{+}]_{Urine}}}}}$

Interpretation

Reference ranges are 3.6–22.6 for SUSPUP and 0.6–5.3 for SUSPPUP.[1]

Increased values support the hypothesis of increased mineralocorticoid stimulation of the distal tubules and collecting tubes, i.e. in cases of hyperaldosteronism.[3] While these parameters have a high sensitivity for screening purposes their specificity may be inferior compared to aldosteron-to-renin ratio (ARR) and potassium concentrations[4]

Both parameters may also be elevated in syndrome of inappropriate ADH secretion (SIADH), probably reflecting a compensatory mechanism, where the organism tries to maintain serum sodium concentrations by means of increased renin and/or aldosterone secretion.[5]

References

1. Willenberg, HS; Kolentini, C; Quinkler, M; Cupisti, K; Krausch, M; Schott, M; Scherbaum, WA (January 2009). "The serum sodium to urinary sodium to (serum potassium)2 to urinary potassium (SUSPPUP) ratio in patients with primary aldosteronism". European Journal of Clinical Investigation. 39 (1): 43–50. doi:10.1111/j.1365-2362.2008.02060.x. PMID 19067735.
2. Yin, GS; Zhang, SL; Yan, L; Li, F; Qi, YQ; Chen, ZC; Cheng, H (13 April 2010). "联合应用血钾血钠和尿钾尿钠的综合指数在原发性醛固酮增多症筛查中的作用 [New index of using serum sodium and potassium and urine sodium and potassium jointly in screening primary aldosteronism in hypertensive patients]". Zhonghua Yi Xue Za Zhi. 90 (14): 962–6. PMID 20646645.
3. Balaş, M; Zosin, I; Maser-Gluth, C; Hermsen, D; Cupisti, K; Schott, M; Schinner, S; Knoefel, WT; Scherbaum, WA; Willenberg, HS (August 2010). "Indicators of mineralocorticoid excess in the evaluation of primary aldosteronism". Hypertension Research. 33 (8): 850–6. doi:10.1038/hr.2010.76. PMID 20520614.
4. Steichen, O; Blanchard, A; Plouin, PF (February 2011). "Assessment of serum sodium to urinary sodium divided by (serum potassium)² to urinary potassium as a screening tool for primary aldosteronism". European Journal of Clinical Investigation. 41 (2): 189–94. doi:10.1111/j.1365-2362.2010.02401.x. PMID 20955208. S2CID 37407685.
5. Knoop, H; Knoop, U; Behr, J; Heyer, CM; Kuert, S; Roggenland, D; Suermann, M; Dietrich, JW (April 2013). "Syndrome of inadequate antidiuretic hormone secretion in pulmonary tuberculosis - a therapeutic challenge". Pneumologie (Stuttgart, Germany). 67 (4): 219–22. doi:10.1055/s-0032-1326101. PMID 23420227.