Plasma Sodium: a Predictor of Perforation in Acute Appendicitis. (The NAP-study)
Plasma Sodium: a Predictor of Perforation in Acute Appendicitis. (The NAP-study)
This clinical prospective diagnostic accuracy study assesses plasma sodium concentration
 using blood gas analysis at the emergency department in children, age 1-15 years, with
 suspected acute appendicitis. The overall assumption is that using plasma sodium as a
 biomarker, a cut-off value of <136 mmol/L will differentiate perforated from non-perforated
 acute appendicitis. In addition, traditionally used clinical diagnostic variables as well as
 radiology used in the diagnosis of acute appendicitis will also be obtained. Histopathology
 will be used to define if the appendix is perforated or not.
Background: The historical dogma that acute appendicitis always progresses to gangrene and
 perforation has been rejected. In addition, there is evolving evidence that medical treatment
 of non-perforated acute appendicitis is safe. On the other hand, perforated acute
 appendicitis requires appendectomy [Andersson]. Therefore, it is important to differentiate
 perforation from non-perforation in order to enable proper treatment.

 In a pilot-study in children with acute appendicitis (n=80), plasma sodium was shown to be an
 independent predictor differentiating between perforated and non-perforated acute
 appendicitis [Lindestam]. Using plasma sodium at a cut-off value of <136 mmol/L, the odds
 ratio of having a perforated acute appendicitis was 31.9 (95% CI, 6.3- 161.9) with an area
 under the receiver operating curve of 0.93. Sensitivity and specificity were 0.87 (95 % CI
 0.60-0.98) and 0.83 (95 % CI 0.72-0.91). Similar results have later been shown by another
 research group [Pogorelic]. Possible mechanism for lower plasma sodium among patients with
 perforation is higher concentration of arginin-vasopressin, which has previously been shown
 [Lindestam].

 Methods: Participants (n=450 in total) whereof 150 in Sweden, 150 in Republic of South
 Africa, 50 in Germany, 50 in Denmark and 50 in Norway will be included in the study. The
 patients/parents will be asked for participation in the study and included after decision of
 surgery has been made by the attendant surgeon. At this timepoint, (i) variables from
 clinical examination/history (presence of right iliac fossa pain, rebound tenderness,
 duration of symptoms, vomiting, temperature, gender, age, weight, (ii) blood sampling: blood
 gas (including plasma sodium), C-reactive protein, neutrophiles, White blood cell count
 (obtained at the emergency department) and (iii) radiology has been obtained. No intervention
 is planned. These variables will also be used to calculate the Appendicitis Inflammatory
 Responce (AIR) score [Scott]. Thereafter, plasma sodium concentration will be added and the
 score will be recalculated.

 After surgery, histopathology will be used to determine if the appendix is perforated or not.
Inclusion Criteria:

 -  Children with suspected acute appendicitis

 Exclusion Criteria:

 -  Chronic metabolic disease

 -  Endocrinological disease