Hi Anonymous,

Thank you for posting an interesting article. It is worth noting initially that the paper relates to data on South Sudanese children and that findings should not be extrapolated given the potential geographical variability in the ratios of children identified by MUAC or WHZ. 

The paper raises several issues that are worthy of critical discussion, however given its focus in the abstract I would like to highlight some of the conjectures regarding the recovery of lean vs. fat mass during recovery and the conclusions subsequently drawn. 

The paper's findings based on estimations of relative velocities of MUAC3 vs. weight gain suggest that initial recovery is marked predominatly by increases in fat mass, that the child remains at risk of mortality following recovery due to lack of recovery of muscle mass and, by extrapolation that the discharge criteria should be changed.

However it is worth noting that loss of fat and low leptin levels also contribute to mortality risk, therefore the deposition of fat during and after recovery from SAM should not be viewed as wasted growth nor as somehow impeding recovery by impeding the growth of lean mass. 

Contrary to the posted abstract, a recently published paper by Kangas et al (March 2020) suggests that following treatment of SAM children with RUTF, there was recovery of lean mass (fat free mass index was not different from community controls at recovery) and that at recovery fat mass was deficient. 

https://www.clinicalnutritionjournal.com/article/S0261-5614(20)30102-3/fulltext 

I have data (unpublished) that tracked the recovery of children admitted with SAM into a CMAM programme in Malawi. We measured MUAC and mid upper arm triceps skinfold thickness in SAM children during treatment  with RUTF. We compared changes in the arm fat index with MUAC during treatment and found that for many individuals there is indeed a relatively rapid increase in arm fat index relative to MUAC at the beginning of treatment. However, the changes were variable between individuals with some not showing any rapid 'catch up' at the start of treatment. The data also suggest that arm fat index reaches an asymptote during recovery for some individuals while for others it continues on a steady trajectory up to the point of recovery. As yet the data has not been disaggregated by age, however the changing energy cost of fat deposition from 0-2 years of age possibly contribute to this variability in the recovery trajectory. 

We also looked at changes in the cross sectional area of muscle and fat during treatment. While the data needs more detailed analysis, it suggests that the cross sectional area of both lean and fat mass in the upper arm both change over the entire treatment period and that the changes are generally well correlated.  However, the relative increases of muscle and fat cross sectional areas in the upper arm also varies between individuals. While I have not analysed the data fully and so have not drawn any conclusions, I would suggest that the hypothesis of fat deposition impeding lean mass deposition, particularly during initial recovery,  is suspect.

The relapse of children following cure from SAM is a complex phenomenon. It would appear logical that if children were treated for longer (i.e. beyond the current discharge criteria) they would go on to gain more fat and lean mass and be more resilient to relapse. However I don't think the paper provides adequate evidence that recovered children remain at high risk of mortality following recovery primarily due to inadequate lean mass gain. Other studies have indicated low relapse / mortality rates following recovery at current recommended discharge criteria.

Discussions of the use of weight for height vs. MUAC and the expansion of MUAC criteria have been debated elsewhere. Whatever your view on this, the potential increase in treatment costs through expansion of the admission / discharge criteria may, depending on funding, also limit the number of children that can be treated and should be decided on a case by case basis rather than as a general recommendation. 

I think there is some caution needed in the interpretation of the data presented in the paper and, as the paper concludes, further research is necessary into body composition during and after treatment for SAM.

Paul

Thanks paul and as you rightly say its a very interesting article giving insights into a different way of looking at CMAM admission and discharge criteria and also provides grounds for further research