Bring a large pot of salted water to a boil and cook the elbow macaroni according to package instructions until al dente; drain and return to the pot to cool slightly.
In a small bowl, mash one egg yolk with a fork. Stir in the yogurt, mayonnaise, and lemon juice until smooth to make the dressing.
Add the dressing to the warm pasta and toss to coat evenly.
Gently fold in the chopped egg whites, sliced radishes, sliced celery, and chopped dill pickle. Season with salt and pepper to taste.
Chill the salad in an airtight container until cold. Sprinkle with chopped chives just before serving.
