Spike-in Control：添加/加入（某种物质）的对照（组）
在某些情况下，待检验样本中不含待测物质或者含有但是浓度很低，为了证明自己建立的方法能对样本中待测物质进行有效的检测，可在待检样本中加入一定量的待测物质（外标）来进行该方法检测能力的验证。有时，这种加入外标的物质，也可用作为阳性对照。
请楼主结合具体的语言环境来确定准确的意思。
以下是对楼下战友提供的wiki中关于RNA Spike-in 解释部分的翻译，不妥之处，敬请指正：
An RNA spike-in is an RNA transcript used to calibrate measurements in a DNA microarray experiment. Each spike-in is designed to hybridize with a specific control probe on the target array. Manufacturers of commercially available microarrays typically offer companion RNA spike-ins "kits".[1][2][3][4]
Known amounts of RNA spike-ins are mixed with the experiment sample during preparation. Subsequently the measured degree of hybridization between the spike-ins and the control probes is used to normalize the hybridization measurements of the sample RNA.
RNA spike-in是用于对DNA微阵列试验进行校正的DNA转录物，这种spike-in可以和标靶阵列的特异性控制（对照）探针进行杂交。商业化微阵列扫描仪的商家一般会同时提供的RNA spike-in试剂盒。
制备样品时，将已知量的RNA spike-in和试验样本混合，然后检测spike-in和控制（对照）探针的杂交程度，用这样的数据对来样品RNA的杂交水平数值进行校正。