| Wall pellitory, IgE | 994 |
| Walleye pike, IgE | 13451 |
| Walnut (F256), IgE | 4217 |
| Walnut tree (T10), IgE | 6795 |
| Walnut tree, black, IgE | 994 |
| Walnut, IgE with component reflex | 994 |
| WANG needle aspiration for cytology | 6301 |
| Warfarin, serum or plasma | 994 |
| Warthin Starry Silver stain for spirochetes | 12376 - Technical only, 12379 - Technical & interpretation |
| Wasp, paper, IgE | 13467 |
| Water chestnut, IgE | 994 |
| Water culture | 6530 |
| Watermelon, IgE | 994 |
| WBC stool | 6608 |
| Weed mix 2, IgE | 994 |
| West Nile Virus (WNV) antibody, CSF | 13530 |
| West Nile Virus (WNV) antibody, serum | 13528 |
| West Nile Virus (WNV), RT-PCR | 13533 |
| Wheat (F4), IgE | 4209 |
| Wheat components, allergy | |
| Whey, IgE | 994 |
| White ash (T15), IgE | 6725 |
| White bean, IgE | 13442 |
| White blood cell count | 514 |
| White oak (T7), IgE | 4197 |
| Whitefish, IgE | 994 |
| Willow, IgE | 13470 |
| Wilms' tumor 1 by IHC | 12376 - Technical only, 12379 - Technical & interpretation |
| Wingscale, IgE | 994 |
| Wormwood, IgE | 994 |