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# Using Road to Health Charts, is a percentile cut-off commonly used to indicate growth problems

This question was posted the Management of wasting/acute malnutrition forum area and has 5 replies.

### Mark Myatt

Frequent user

31 Jan 2014, 11:29

You would not really want W/A to drop much below -2 z (roughly P3). The usual approach with GMP data is to look for deviations from the expected growth curve. A child may track the growth curve even when they have a low W/A. This is usually OK. Dropping away from the growth curve is "growth faltering". When you see this then take MUAC. If MUAC is < 115 mm then refer to CMAM. If MUAC >= 155 mm then counsel and refer to appropriate support services.

### Mark Myatt

Frequent user

31 Jan 2014, 11:31

Oops ... meant 115 mm. Not sure why the posts appears twice.

### Mark Myatt

Frequent user

31 Jan 2014, 12:58

The reference distributions are very nearly normally distributed so you can expect (e.g.) P16 to be at -1 z-score (we often use P15) and P2.5 to be at -1.96 z-scores. Here is a short table showing how z and p are related: ``` z p ---- ---- 0.0 0.50 <- P50 -0.1 0.46 -0.2 0.42 -0.3 0.38 -0.4 0.34 -0.5 0.31 -0.6 0.27 -0.7 0.24 -0.8 0.21 -0.9 0.18 -1.0 0.16 <- P15 (or thereabouts) -1.1 0.14 -1.2 0.12 -1.3 0.10 -1.4 0.08 -1.5 0.07 -1.6 0.05 -1.7 0.04 -1.8 0.04 -1.9 0.03 <- P3 (or thereabouts) -2.0 0.02 -2.1 0.02 -2.2 0.01 <- P1 (or thereabouts) -2.3 0.01 -2.4 0.01 -2.5 0.01 -2.6 0.00 ---- ---- ``` Software like EpiInfo, ANTHRO, ENA, &c. will calculate z-scores and percentiles for you. Tables are available ... for example that give percentiles: http://www.who.int/childgrowth/standards/en/ Any help?