List by countries purchased COVID-19 test kits in 2018

About "World Integrated Trade Solution" (WITS)
The World Bank — in collaboration with the United Nations Conference on Trade and Development (UNCTAD) and in consultation with organizations such as International Trade Center, United Nations Statistical Division (UNSD) and the World Trade Organization (WTO) — developed the World Integrated Trade Solution (WITS).


[link to wits.worldbank.org (secure)]

I think you are taking this out of context. Read it properly, you will see it says:

Instruments used in clinical laboratories for In Vitro Diagnosis. Colorimetric end tidal CO2 detector, sizes compatible with child and adult endotracheal tube. Single use.

So, it is talking about the EQUIPMENT used during the tests. This is equipment already used for other things too. This was not published like this in 2018.

Basically, you have completely misunderstood the site.

If COVID19 first appearing in 2019, then why were $100 BILLION worth of testing kits, purchased in 2018?

[link to wits.worldbank.org (secure)]

At the top it says:

COVID-19 Diagnostic Test instruments and apparatus