Hi Anonymous,
The discharge criterion should be the same as the admission criterion. A child should not be admitted on one criterion and discharged on another.
The average LOS in outpatient care for a child with uncomplicated SAM will likely be similar for MUAC and WHZ (approximately 6-8 weeks) depending on the cut offs for admission and discharge used and rate of weight gain.
The absolute differences in measurements between sexes in children of the same age (for MUAC) or same height (for WHZ) is very little (1 - 2mm for MUAC) or (+/- 100g for WHZ) so I wouldnt expect to see much of a difference in LOS based on sex alone. With the absolute cut-offs we use, the bigger effect on length of stay (LOS) is likely to be due to the degree of malnutrition on admission, the presence of other illnesses or dehydration, and compliance with attendance and treatment protocols (and thus rate of weight or MUAC gain).
For example, a child with a MUAC of > 110mm and no illnesses on admission, with full protocol compliance, may acheive a MUAC > 125mm within about 4-6 weeks (average MUAC gain is around 2mm per week). The same child with a MUAC of less than 100mm may take approximately 10-12 weeks. For a child with oedema the LOS will depend on the severity of the oedema on admission along with the other factors described above.
Short children (< 65cm tall) tend to experience longer stays than taller children, see:
https://archpublichealth.biomedcentral.com/articles/10.1186/s13690-016-0136-x
There may also be some variation in LOS depending on the specific criterion for discharge recommended in national guidelines. For example, some national guidelines may recommend WHZ > -2z or > 1.5z or > -1z for discharge; the LOS will increase accordingly.
More recently simplified treatment protocols using adjusted doses of RUTF depending on absolute MUAC during recovery may also affect the LOS by virtue of a change in the rate of MUAC / weight gain. (please see the links to articles in the previous reply from Marko).
I hope this helps,
Paul