WoW:API LootSlotHasItem

Returns

isLootItem

Boolean - is it a loot item instead of a coin

Example

Iterate through the items in the currently opened loot window an display them in the chat frame, side by side.

local itemLinkText
for i = 1, GetNumLootItems() do
    if (LootSlotIsItem(i)) then
         local iteminfo = GetLootSlotLink(i);
         if itemLinkText == nil then
              itemLinkText = iteminfo
         else
              itemLinkText = itemLinkText..iteminfo
         end
    end
end
DEFAULT_CHAT_FRAME:AddMessage(itemLinkText)