A boy age 6 years, weight 13 kg. PEM grading
**Core Concept**
The question is testing the knowledge of the Waterlow classification, a widely used method for assessing the nutritional status of children. The Waterlow classification involves calculating the percentage of the expected weight for a child's height, which is then used to categorize the child into different levels of malnutrition.
**Why the Correct Answer is Right**
To determine the percentage of the expected weight for a child's height, we need to calculate the expected weight for a child of a certain height. The expected weight can be calculated using the following formula: Expected weight (in kg) = 2.3 (age in years) + 4.5 (sex) + 0.3 (height in cm). However, this formula is not directly used in the Waterlow classification. Instead, we use a chart that provides the expected weight for a child of a certain height. Once we have the expected weight, we can calculate the percentage of the expected weight for a child's actual weight. The Waterlow classification categorizes children into four categories: Underweight (less than 70% of expected weight), Normal (70-90% of expected weight), Overweight (91-120% of expected weight), and Obese (greater than 120% of expected weight).
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide a clear calculation or categorization of the child's nutritional status.
**Option B:** This option is incorrect because it does not provide a clear calculation or categorization of the child's nutritional status.
**Option C:** This option is incorrect because it does not provide a clear calculation or categorization of the child's nutritional status.
**Clinical Pearl / High-Yield Fact**
To quickly estimate a child's expected weight, you can use the following formula: Expected weight (in kg) = (age in years x 2.3) + (sex x 4.5). This can be a useful shortcut when using the Waterlow classification.
**Correct Answer: C. 70% of expected weight is the definition of underweight according to the Waterlow classification, which applies to children aged 6 years old and 13 kg weight.**